I learned this for my dad many years ago and it works great. It also saves a trip when I ruin a gasket.
Lay your gasket material in place and use the ball end of a ball peen hammer around the perimeter of the casting/plate/other part. Lightly +-use the hammer (you know like Maxwell) and the gasket material will cut as with a knife. Use the same procedure on the ID of the gasket. For the holes make sure the cut gasket doesnâ€™t move and peen the holes. The hammer will cut a nice hole. Larger holes are easier. Smaller holes require a smaller hammer.
For cork gaskets I use a utility knife to cut the shape of the gasket and thin wall brass tubing to punch the holes.