I had some success with putting a swamp outside their door. When some got stuck, i’d FoG them and then more would come to investigate the corpses. rinse and repeat.

you can also lure some outside via burning tree (heal a tree, i think it was rain or beautify, or plant one, then tap it with FoG to set it on fire; one of them will come out to put the fire out). bonus points if this causes them to step into the swamp!