Leather (or any material you like.)
Fake sinew (or string/thread.)
Sewing machine, or needle if sewing by hand.
Leather punch (if working with leather.)
Decorations: paint, beads, stones (Optional)
First cut 2 pieces of your leather or material into a square or a rectangle any size you want your pouch to be. (make sure these two pieces are the same size.)
Next, place the material face to face (this means if you have a pattern on your material, you want the pattern on the inside of your bag at this time.)
Now, take your needle and thread, or use a sewing machine, and sew around three sides of the pouch. Be sure to leave one side open, this will be the top of your pouch.
When you are finished sewing, use your scissors and cut the thread off.
Turn the pouch inside out. If you used a pattern on your material, your pattern should now be on the outside of your pouch.
To close the pouch, you can either use string, and just tie it around the top of the pouch, or you can cut small slits in the material and weave a string through the slits. (I don't recommend this on thin material.)
Your bag is now done, all you need to do is decorate it if you wish.