You can use some of the crypt entrances as mini camps. I actually turned one into a base for a while. You can fit a bed and workstation in under the entrance rock of the big stair ones. The stand alone ones can fit a bed and workstation as well. Couple of walls and a door and your done. I tend to put the fire outside and house it separately although the one in the wide stairs I had the fire inside as well. The hole in the wall type ... not really anything I could figure out easily to use.

You can also tunnel under big boulders or just dig a deep enough trench to keep out the enemies.

https://steamcommunity.com/sharedfiles/filedetails/?id=2509631140

This base is under a large copper deposit.
https://steamcommunity.com/sharedfiles/filedetails/?id=2509633689