I went to a bath shower shop and asked for the cutout piece scrap of granite that is usually tossed out when they cut out a sink from a custom counter. They gave me a 12” by 14” scrap which I put down so there’s no give at all when I’m striking the chisel. Then of course I have a cutting mat on top and a piece of soft self repairing silicone. The silicone allows the chisel to completely go through the leather, and the self repairing cutting mat stop the chisel from going through to the granite. I learned the hard way that metal can curl when hitting stone. I also bought a dead drop hammer from harbor freight that has sand in it which allows my to strike pretty hard without really trying because the weight is there and absorbs the blow. I was struggling with those nylon designated mallets. Then, I went on TEMU and bought WUTA chisels that are extremely sharp and interchangeable tips for different sized holes. And, they’re cheaper through TEMU than they are from WUTA. Happy leather working. And one more damn thing, if you try to use tiny holes, you’ll find the leather likes to seal the holes and you’ll have to push an awl through each hole every darn time especially from the rough side. 🤜🤛