Minecraft wiki entry for Wither_skeleton_farming, associated text: In this method you use an iron golem to lure wither skeletons into a falling trap. This trap can be upgraded with pistons to push wither skeletons through a portal and then be blown up by a charged creeper. This is a very cheap method but only gets about 5 skulls an hour but with the modifications it can get a skull every minute. It is meant to be used as an alternative to grinding for skulls and not meant for killing the wither multiple times. This method is for all platforms but the modifications with the charged creeper is more effective on bedrock edition.