I'm total newbie and I don't know how to make killboxes, but what I did on my newest colony is working great so far, I made the base close to a mountain and one big corridor and I just let the door open. Instead of making walls far from the base which the raiders like to tear down.
As they enter the base I'm there waiting to shoot them and I leave some melee guys behind a door, as soon as they pass I attack them from behind. I also like to leave some crops just outside the main door and they like to put it on fire losing time and closing their only escape path.
It's great in winter too since I leave some kibble in there and starving animals rush to eat it and I just hunt them inside the base.
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As they enter the base I'm there waiting to shoot them and I leave some melee guys behind a door, as soon as they pass I attack them from behind. I also like to leave some crops just outside the main door and they like to put it on fire losing time and closing their only escape path.
It's great in winter too since I leave some kibble in there and starving animals rush to eat it and I just hunt them inside the base.
[attachment deleted due to age]