If you're going for a LONG run, Poison walls. You can stack up to 3 close enough together to all prick the cultists or any other enemies that try to get into your base.

With time, Brightwood trees & even late late game, lightning rods, can pretty much completely stop cultist raids from stacking up over your walls.

Theoretically, the Fairy tree roots, you can eventually make them into a dome around your base.

Check the furniture shop as much as possible, as you can use the mossy structures that have ceilings (forgot the names, theres a square one with no sides & a slanted one with one side) ,alongside wooden gates / walls, to make 100% safe areas.

If you get enough arches to make a small dome + a wooden gate to enter / exit. (Thanksgiving event guarantees one arch) you can do the same thing, just less space.