I have small bases everywhere they're convenient but my mains are usually on peninsulas near black forest and swamp zones.

My first base was on the top of a large hill and nothing could climb it but me so it was super safe.

I've also built islands to put bases on. I'll search the coastline with my boat and find a shallow spot or a spot with a tiny amount of biome sticking out of the water and start building it up until I can use it.