I tried three different ways to kill witches in my farm. At first I put campfires but she would keep splashing herself with potions. Same thing with a cactus. I tried a drip stone, but at the distance she needed to fall, she’d despawn. Finally, I came to this arrangement. Will she somehow be able to cheese this one too? I’d like to leave it overnight tonight.
Campfire is just for light, she drops down, is forced into the boat, which suffocates her in the wall. Skeletons occasionally end up in the witch hut but I’m pretty sure I’ll only get one witch at a time.