Easiest two solutions:

1) Build at an island. Raise the land and build upon that.
Most things won't spawn there anymore, event spawns may approach you but unless you provide some access, not even being able to enter your base. Flying spawns excluded from that.

2) Build at a hill and dig a trench around it. Start the trench at least 8 meters from your outside walls, place hidden campfires along the walls to prevent closer spawns,

This may perhaps not stop most monsters, but it would at least stop most of them.
There are some nice tricks to make it easier for you to cross the moat, of which the "gate bridge" may be the one most time consuming, but certainly the best defence.

Thorin :)