yeah i've made a couple. the first one just had a slanted plywood floor, which worked fine at first but over time the
chickens' claws wallowed out the grain of the plywood and the eggs would hang up on it. The second one I made also had a slanted plywood floor, but each nest box has a removable kitchen cutting mat covering the bottom, which stands up to their claws and is easy to remove to clean off any
chicken poop or anything else that gets stuck on there.
There's not much to say other than they're just a box that's tilted, with a little opening at the bottom and a tray to catch the eggs.