If you cannot defeat the swamp enemy easily bonemass is way out of your league, find another swamp to gear up. Once the swamp enemy are trivial to you, then build your outpost.

to build an outpost (a portal, a bench, a chest, maybe a fire, not much here) just raise walls with the hoe and throw up a pole to glue a roof on it all. you can RUN up hoe-walls so you don't need an entrance or exit.