Jud, just imagine a square of leather. Stitch the edge of a wide piece of elastic to the edge of one piece, then do the same with another peice of elastic on the other piece of leather. You are left with two separate pieces of leather with elastic at one edge. Place pieces grain to grain, line up the edges and then run a stitch down the elastic leaving as of a "margin" as required. Fold the two pieces flesh to flesh and voila! Now do this for 3 sides instead of one and you are done! Of course you will have to turn the item inside out at the end instead of folding.
Cya!
Bob