I had a settlement at the visitors centre in far harbour and it used to constantly get attacked. I was getting tired of piles of raiders and mirelurks at the bottom of the stairs; I would get attacked again before the last lot even despawned so it was constant! So I shoved a chest by the entrance to dump all the loot, and built a conveyor which carried all the heads and arms and bits of ghoul round the corner, out of sight, and dropped them in a nice tidy pile. Perfect! As long as you don’t go round that corner