Originally posted by Latcady:

I've got an under a big rock base & an under an Elder spawn base, both work fine and you get some really fun organic feels with the under a big rock approach. Just one caution digging under a rock, it's super easy to accidentally chip a section out of your rock, so go slow.

I've gotten lucky and found copper nodes and large boulders in contact with each other in hilly Black Forest areas. As you said, go slow and you can whittle out some decent sized pockets with stone roofs. However, I believe a Troll is capable of bringing down the house! lol