Yeah it would probably be easier to make it from some plastic container (you're not going to see the bottom part anyway) and cover the lid up so that you don't see the plastic. If i use a somewhat shallow bowl it will be easy to clean out as well. Also it will make having different sizes as it grows easier. So the underground part is all right then? (It should be no problem as they usually use underground burrows in the wild)

By the way, about how much weight should I put on top of the lid to keep the snake from lifting it up?

Thanks so much for answering my questions, I am crossing both my fingers and toes hoping that reptiles will be legal here in Norway soon.