I'm a first time leather hobbyist and have purchased the Beginner's Starter kit from Tandy, In the accompanying DVD, they show that to make a leather wallet, one should glue a piece of cardboard behind the leather to avoid it stretching and deforming during the stamping process. The supplied contact glue was used to do this. Can anyone recommend the best way to later remove the cardboard without leaving a messy glue residue with bits of cardboard attached?