video here: https://inv.nadeko.net/watch?v=IQxZ9Sv68Jg
Or, here, if you’re nasty: https://youtu.be/IQxZ9Sv68Jg
Well you don't let them out. It's more like a prison that they willingly go into thinking it is one thing but isn't really.
Shallow ditch does sound like a good option, wicker basket full of heads is also satisfying.