Before starting into any stamping, the leather must first be wetted to soften it. I simply use a spray bottle filled with clean water and spray down the leather. For stamping, you don’t want the leather sloppy wet or mushy, but just damp. If you are new to leather work, it is always best to practice stamping on a scrap first before launching recklessly into the real thing.
If you are doing very much stamping, you may have to re-wet the leather occasionally during the process. It is a good idea to wear safety glasses while doing your stamping, particularly if you are using a steel hammer to strike the stamping tool as I am here. (Many leather workers use a wooden or rawhide mallet for striking leather stamps).
I recommend that you do your stamping on the most solid work surface that you can find. I use a smooth concrete patio slab that measures about two feet square by about 3 inches thick. This sits on a big wood stump from my firewood pile, on the cement floor of my shop and is just the right height to sit at while working.
In the image above, I am using a leather stamp that I handmade in my shop from an old bolt.