A complete base defense has 3 components:

1) Work bench coverage to prevent spawns inside your base
2) An earthen barrier to prevent mobs from walking into your base (trench works fine, you can raise the ground with a hoe to do the same thing, or flatten the outside of your trench for a nicer look that leaves your base on elevated ground)
3) A wall to break line-of-sight from the outside so mobs don't aggro on you or your base structures.