You should create some secret places, like on the map Esseker if you explored. There is a mountain where you can enter inside from top or bottom.

Some examples are caves around the islands at the sea level, where we can build bases on Exile servers (important is to be reachable by a Hunter for example). Caves in mountains, somewhere hidden where are bushes and high vegetation. Closed mines that have a little space inside the rocks of the mountains, where a base could be build.

Here are some examples of different types of sea caves:
Sea cave inside
Cave at sea level
Open sea cave