What you need:
A piece of leather, approx. 12" x 12" (I bought a piece 24" x 24" at Dressew here in Vancouver for $7)
Utility knife (and something to cut on, like a self-healing mat)
Needle & thread
Template: You can draw a template freehand, or you can go here to print out the template I created.
*Print the template on heavy cardstock.