A good base is not thick walls. It is a path you control, a fighting position you can hold, and an exit you can still use when things go wrong.
Choosing the spot
Build near a trader and water, on flat ground. Flat ground keeps zombie pathing predictable, which is the whole point.
Layers, not thickness
An outer wall to slow them, a killing corridor, then an inner hold. One thick wall gives you nothing to fall back to when it breaks.
Structural rules
Support matters. Blocks without a load path collapse, and a collapse during horde night ends the run. Upgrade from the ground upward.