Built-in is a really easy way to place a zipper, they can go on wallets, handbags, jackets.
What you will need
2 x 27x27cm cotton or other external fabric
2x 27x27cm PUL
How to do this project
Place the slippery side of the PUL with the right side of your fabric
Sew around the rectangle
Cut the middle line and cut a triangle on the end
Turn the PUL to the right side
Use pins to hold the zipper in place and sew around
Place the right side of the fabrics together and sew them separately(PUL+PUL and Cotton + Cotton). Remember to leave one part open on the PUL side, so you will be able to turn them to the right side (and also leave the zipper open).
Turn to the right side and close the opening