You can build a little oval stake wall and roof in front of burial chambers and frost caves. Then you are nice and snug with your portal and a chest inside. Set this up towards end of day, explore around that area a bit, go home for night and do the bc the next morning, strip down the set up and move on to the next one.
On burial chambers that are all above ground there is an overhang on the side your workbench fits in that makes it usable and noone ever attacks it, even angry trolls.

Stick your portal and even make a base on top of sunken crypts. Abominations wont attack you or the setup you build up there. I have been attacked by a wraith once on top of a sc but that's it.

There is (somewhere) a great video on understanding how building works, the progression from beefy blue to broken red build items that is really important. There are specific things to look for as you build and it's too long and involved to go into here. Google is your friend. Oh, and most of the most amazing builds are done in a special mode, not in vanilla game.