get thin pig or goat - remember the pad needs to be thinner than the stock by the thickness of the leather -

take your time, you need to be able to stretch the leather just a bit, but not enough to compress the pad. smooth it out as you go, and cut the notches a litle at a time to allow the bottom to sit smooth on the butt. I did mine from instructions posted on this board a long time ago - 10 years or so.