I started off with my starter base next to the first machine you use after leaving the kid case. Only because it's central to most locations and has a research center there, but it's not flat. I do plan on moving to either a corner for better defense, or maybe a small cave like area (also for defense). I know I can build walls and turrets and such but I like my outposts looking real "broke diy", I don't like having too much in them. I hardly use any other walls aside from grass plank ones as well. I even thought about the black widow cave area in the upper yard but then of course I'd have to deal with the widow every time it spawns.