If you go to www.messynessychic.com you will find a delightful array of archived photos of various kinds of shelter carved out of tree trunks, mostly from the giant sequoia found on the west coast of the U.S. There are also some descriptions of who created them and how they were used.
This is amazing. How did they carve out the stump?
Well. these were mostly created before the days of chainsaws, so I imagine that they use axes, hatches, chisels and such.