How to Sew a Professional Bag Flap

Deets peeps – The Devil is in the details – doesn’t matter how you say it, details matter. In everything actually but in sewing it is super important. Details are what make the difference between a good maker and a great one. Today’s particular detail is the flaps on bags. And bag pockets for that matter.

The bag flap gets a lot of work. Chances are you will be opening it a lot to access your bag so you want it to be strong and durable. This means interfacing. Interfacing is actually like good underwear for your bag – you know the difference between a great bra and that old saggy one that is grey and held together with blue tac? You need to use interfacing and in a bag flap, you will ideally need to use several layers and several types.

As you may know, I have been writing patterns for my Etsy shop and while I was writing the latest, it occurred to me that it is all very well to blithely rate a pattern as ‘intermediate’ or ‘confident beginner’ and then just leave people to assume what that actually means. What happens to people who fall through the cracks – they may not be a raw beginner but they still need a bit of help when it comes to construction techniques. The trouble with sewing is that it isn’t regulated. There is no core body of knowledge that is taught everywhere so even an experienced sewist may never have used a technique where a beginner may use it quite a lot. The knowledge of a sewist can be all over the place.

So I thought that the best way to be helpful is to choose a technique and focus on it in a sort of user-friendly masterclass. And this time, it is all about the flap on a bag or pocket.

To give it real world relevance, I will be linking it back to a pattern (The Pasadena Shoulder Bag) so that you can see what the technique looks like in real life and where it would be used. You don’t have to buy the pattern and the tute is free. You can use these techniques in any pattern.

Okay, so we will begin with a tute on how to create a professional bag flap. It has a few layers which may surprise you and the result is a bag part with a really nice feel to it which doesn’t look sad and forlorn.

So what do we need to make a flap for a bag? You can substitute the following items for any pattern but for reference, as I mentioned, I will be referring to my pattern so that things do not get too confusing (for me too!).. I use Vlieseline products. It is important to mention that here because some of their things do not have actual names, instead they have numbers and for a beginner, it can be quite confusing. So you need:

  • H630 (see what I mean about the numbers!). This one is a light, low loft fusible fleece.
  • Decovil I Light. A light but softly structured fusible interfacing.

So we only need two types of interfacing but it is the way that we will be layering them that counts as the real trick.

Begin by cutting out your flap outer piece. There will mostly be a template for this but occasionally in a cut and measure pattern, you just cut a shape. And cut the lining piece without trimming it to the shape of the flap. This is quite important and I will get to that in a minute. The pattern will give you the sizes and details.

Now fuse the appropriate piece of H630 to the flap and the lining. This gives your flap a nice soft feel when you use it. Okay – trick number one, fuse the piece of Decovil I Light over the top of the fleece on the cutout flap outer.

This adds structure and it will end up being sandwiched between the flap outer and the flap lining both of which have the fleece there to keep things soft.
So you have two flap pieces, and one is still untrimmed. With the right sides together, lay the trimmed flap outer onto the untrimmed lining. I have trimmed my Decovil I Light back here to reduce bulk but for goodness sake don’t be as lazy as I was and make a nice clean cut! It won’t actually matter in the finished make but boy does it draw the eye!

Anyway, pin it well and get ready to sew. Before we do though, there is a very good reason for leaving the lining untrimmed. Fabric shifts. This is a matter of physics and not much you can do. It is thanks to friction. By leaving the lining whole to begin with, you guarantee a perfect fit and none of the frustrating running off of fabric that can happen when you cut the flap and the lining to fit. You still have the flap outer as a shape guide.

The next step is to sew it and cut it out using the flap outer as a guide.

There is a tiny bit of waste but nothing too bad and it is well worth it to get a prefect flap.

Now there is a turning gap in the straight part of the flap at the back but if we turn it out now, the front curved edge will pucker because there is way too much fabric there. When it is turned the right way out, the fabric has to negotiate the curve of the flap from the opposite direction, causing it to form a sort of frill. We have to get rid of some of the fabric.

You can see the little cuts there on the curves? This is how we get rid of some of the fabric and give what is left some room to move. Just make these with a small and sharp pair of scissors being very careful not to cut the stitching. Clip across the corners at the back too.

Here is a closer look at the snips, known and ‘notching’. The interfacing actually helps to keep them neat and stable.

When the flap is turned the other way (the right way) out, they will all butt up together to smooth the curve, sort of like a mitre.
Right, so turn the flap the right way out and press it so that the edges are perfect. This means that you cannot see the lining from the bag outer and you cannot see the outer from the lining side. Spend time and use a damp cloth to get a great result.
Then we close the gap. I have pressed mine here and it is ready for a bead of glue just to hold it closed when i get to the sewing on bit.

You don’t want to stitch on the back just yet (more in just a bit) so a dab of glue will hold the back shut while you work on the rest. There is a lot of glue involved in bag making. It helps to stabilise things when you do not want an extra row of stitching. 

The next step is to topstitch. You will ideally have a perfect edge like this after pressing with a damp cloth as outlined above.

So the next step is to topstitch to keep it there. Sew the sides and the front of the flap only

The reason for this is that we will topstitch the flap onto the bag and if you topstitch the back now, it will be stitched twice. This can look really clunky. This is why we glue the back shut to keep it in place too. We are saving the topstitching.

Not all bags have a flap attached like this one. Some have the flap integrated into the back seam. The individual pattern will guide you here but as a rule, in those cases, keep the back open. The raw edges will be hidden in the seam.

Hardware next! This is a really exciting bit because all of a sudden, your bag will start to look really professional. If you are using a stud, it will have a male and a female half (I know, I know but just look at the pieces and you will see why they are called that). We need to add the female half to the bag flap at this stage.

The male half goes on the bag front and that will happen later in the pattern.
So we have one final task and that is to topstitch the flap onto the back panel of the bag.

I usually use a double row of topstitching for this. It is stronger and it looks nicely finished.

Okay! there you have it! It is actually easy to make a flap like this and once you try it, you will use the technique again and again. The principle is similar for pocket flaps too although, sometimes and depending on the fabric, the interfacing layers may change. The pattern will tell you what you need anyway. You only need to know about the technique and you do now!

if you have any ideas for a masterclass that you would like to see, leave me a comment in the section for that and I will see what I can do.

Happy sewing!

Debbie xx