I built "emergency" nest boxes out of recycling bins, and my hens loved them! These are stackable bins like storage bins, about 16 by 20 inches, as I'm not sure they are used throughout the country like they are here. I put one up on 4 by 6 timbers, and screwed a plywood top on it. Now that I've put back the original nests (new coop), they actually seem to prefer the recycling bins!