You can use the hoe to raise an earthen berm around your base. The earthen berm is indestructible. You can use the pick to dig a dry moat on the other side of the berm. 3 tiles down is enough. Stuff will sometimes fall into the moat and its pretty easy to kill that stuff with a bow or if you want an impregnable fortress you can put another earthen berm outside the dry most then you only have to put a core wood beam across the moat to use as a bridge. When you want to take a cart across you just have to build floor tiles across the core wood beam and then remove them again when you get the cart across. That will stop all ground based raids.

Ariel raids can be slowed down by placing a roof on every building inside your base (ie: make your livestock pen and bee apiary into barns)