Well... if you want a permanent base, you'll want room for the bed, storage, the cooking pot and mortar and pestle (which can be placed on a table), the forge and the smithy. Although they might be fine outdoors too... Edit: and the fridge, don't forget the fridge!
I made a small cottage (2 foundations) on my raft. I'll put in a bed and a storage box (that I got from a loot crate) and probably a fire... (well, the last might be outside). I killed some trilobites with my metal axe and got 79 chitin from the three of them! I got the engrams for making chitin armour but I can't see it in my crafting menu. Which is ironic since I can see everything else, even if I can't make it....
EDIT2: It's made in the smithy (duh! It said so when I unlocked the engrams!)
Oh! and I just realised I MUST have a fishing rod for my raft! I tried shooting fish with bow and arrows but that just earned me one of those bird attacks...
EDIT3: I missed the place on the beach nearest to my house as I returned from my trilobite hunt. So I figured I'd make one of those small wooden signs to put on the beach.... But I seem to have misread (come to think of it, I haven't unlocked this engram...
so I've done the impossible...)