This isn't extremely fancy, you could do this to teach young girls how to make their own purses, or zipper bags.
Step 1: Materials
Mine has the following measurements :
4 rectangles of 20cm x 15 cm (7.8 inches x 6 inches) and a 6 inch zipper.
2 white, for the inside and 2 black for the outside.
You can do this whatever size you want, if you want it smaller, do so, and it would also fit a phone, it could be a simple wallet, or a tablet case. Whatever you chose to cover or put in it.