This is auto farm for Witch Hut with Ghost appearance and supported for 1.15+. It has to be placed overlapped with Witch Hut, you could refer the last picture of inner structure, there are 3 layers insides, which are supposed to cover the Witch Hut you found. Then, you just stay around in and out for that witch spawned and killed automatically, after you could go down chest room under water to gather items. Besides, there is a little trap door under the Ghost face and upper the chest room, which allows you to go inside to see. Of course, it has to be very dark to make the mobs spawning.
Another usage is to place this farm in anywhere to farm normal "2 blocks height single block" mobs, e.g. no spider, no slime, etc
Note: for using WorldEdit, please make sure you paste with entity, i.e. //paste -e