I have a block of 1018 steel I bought in a moment of dubious judgment. I'm thinking I could get a piece of tool steel plate for a few bucks, drill holes at the corners, harden it, and bolt it to the block. I don't see how I could weld it, because I assume welding would anneal it, but I would end up with over 4" by 12" of flat, hard steel to fool with while I think about real anvils. I would just have to avoid hammering over the bolt holes.