I use a redstone clock here. Redstone clock is the heart of any redstone machine, if the admins are trying to remove the redstone clock, redstone will be over. Why I said it, before you can do the regular AFK build, but after the update, the avatar can't be moved by water if the avatar is standing next to a slab.
So anyway, here is the link: https://youtu.be/Bu1T5sQ4odk
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I watched it and its amazing it makes it so easy