Stone carving system - remove chunks of mesh? Compare two meshes?

I have an idea for a very specific type of crafting interface I want to try for stone knapping (banging two rocks together to get a spearhead in this case).

1 - I know about slicing meshes, but is it possible to remove chunks from the mesh? Like a cookie-cutter imprint for example? Hopefully, the picture explains it, but I want the player to be able to rotate around the target rock in 3d and manipulate their knapping stone to try and punch out chunks from the main rock.

2 - On top of that, I’m also curious if there’s a way to compare the new mesh that would be created to a template mesh. Basically, the closer the player can match the template, the better the item is (in-game stats).