What you'll need:
2 fabrics
Interfacing or fusible batting
Thread
Zipper
Basic sewing supplies (sewing machine, zipper presser foot, iron, pins, scissors)
Lining fabric - 2 pieces of 23cm x 19cm
Outer upper strip - 2 pieces of 23cm x 9.5cm
Lower upper strip - 2 pieces of 23cm x 12cm
Zipper tabs (same as upper strip fabric) - 2 pieces of 2.5cm x 7.5cm
Interfacing or batting - 2 pieces of 21cm x 17cm (with the corners trimmed off)
Take the two zipper tabs and fold in the short ends by 1/4inch and press. Then fold in half and press.
Place the end of the zipper tape up into the fold, and do 2 lines of stitching across to secure. If using a metal zipper, be careful that the needle does not hit the zip as it will break. To sew across the side with the zipper pull, you will need to open the zipper. Use some pins to secure the tape so it doesn't come apart whilst you are sewing.
Trim the excess fabric from the sides in line with the zipper tape. Then cut the tab along the fold line. Fold the two sides of the tabs back and trim the zipper ends. Don't cut too close to your stitching as zipper tapes fray easily and it will come away from the stitching.
You zip should now measure exactly the same as your fabric (23cm). If it doesn't, trim either the zip or the fabrics to match.
Place one upper outer strip and one lower outer strip right sides together along the 23cm side, making sure the raw edges match. Sew across, leaving a 1cm seam allowance.
Press the seam to one side. With the right side facing up, topstitch (increase the stitch length slightly for this) approx. 2mm from the seam line, catching the seam and one strip. This keeps the seam flat. I chose bright pink thread as a decorative stitch. Repeat for the other 2 strips.
Trim the corners off the batting or interfacing. This is to de-bulk so you can get sharp corners at the end.
Fuse to the wrong side of the outer panels. The interfacing/batting is cut slightly smaller than the fabric so place it in the middle of the fabric. This is so the seams are less bulky. The rough side of the interfacing/batting is the adhesive side and so should be placed onto the back of the fabric. Light weight interfacings can melt easily under the iron so use a pressing cloth or turn the panel over and iron on the fabric side. Some interfacings need quite a lot of heat to fuse so don't give up if it's not sticking. Interfacing or batting is not essential but gives the purse a bit more stability.
Note: I fused my batting to the lining fabric as my outer fabric is heat sensitive.
Attach your zipper foot onto your machine now. Notice that the zipper foot has two bars (one on the left, one on the right) that can attach to the machine, unlike the normal presser foot. This is to sew on different sides of the zip. Attach it on the left bar for now. When you have the foot attached on the left side you should always sew with the zipper teeth on the left side of the foot. This is so the foot runs alongside the zipper teeth and not on top. Be careful that your needle is in the correct position and doesn't hit the foot or the zipper teeth.
Place your zip, right side down onto your upper fabric strip so they are right sides together and the edges are aligned (the zipper pull should be on the right hand side). Then place the lining fabric on top, right sides down. Pin along the edge. Using a fabric glue stick is also quite handy here.
Stitch the three layers together. You should aim to stitch about 8mm (very precise!) from the raw edge. If you stitch too close to the zipper teeth, the fabric will get caught in the zip and won't open. When you get about to about 7cm from the edge, stop and open the zip, then continue stitching to the end. The reason for this is that you won't be able to stitch straight past the zipper pull as it gets in the way.
Once you have done this flip the fabrics over so they are wrong sides together and press the fabric along the seam. Topstitch along, catching the 2 layers of fabric and the zipper tape, approx. 2mm from the seam. Again, you can increase the stitch length slightly for this. Repeat for the other side of the zipper - remember, the outer fabrics should always be right sides together and the lining fabrics should be together. If they are not the. Something is in the wrong place.
Open the zip to half way.
Flip the fabrics over so that the lining fabrics are right sides together and so are the outer fabrics. The zip should now be in the middle. To flatten the zipper you need to push it into a U shape, with the bottom of the U coming towards the lining. This is important. Pin to secure all the way around. If you haven't sewn both sides of the zip exactly the same, the fabrics might not be lining up perfectly. You can trim them slightly but try not to trim too much off the sides as you need the tabs to stay the size they are to get nice corners.
Sew around the four edges with a 1/4inch seam allowance (don't make the seam allowance too much bigger than this). Leave a 2inch gap in the bottom of the lining piece so you can turn it the right way out later.
* If you want a flat purse, skip the next step.
To create a flat base, you need to square the corners.
Pick either one of the lining or outer corners and make a triangle so that the side seam and the base seam are matched up and in the centre of the triangle. To match the seams up perfectly, snip the seam allowance at the corner to allow the seams to be pushed in opposite directions then pin.
Measure 1.5inches from the tip of the triangle and draw a line across (the deeper into the triangle you stitch across, the wider the base of the purse). Trim the excess fabric off, leaving a 1cm seam allowance. Repeat for the remaining 3 corners.
Open the zipper the whole way and turn the purse through the hole that you left in the lining so that it is right side out.Stitch the hole closed. Push the lining inside. Use your fingers to pop out the top corners where the zipper ends are (it will feel stiff)
Done! Try with laminate fabrics to make a washable makeup bag!