Looking at the finished product at the end of today tells me I forgot to slope the roof which would prevent roosting thus eliminating the chore of scraping off the top of the nest box each time we added new bedding material.

We repurposed old milk crates by nailing them to the coop wall, and then covering the plastic with a decorative burlap fabric. They are about 3ft off the ground, with the opening pointed up, so that the chickens climb down inside it. The burlap on the plastic rim of the crate makes it very hard to hold onto without slipping off, thus deterring roosting.

We have a bank of six nest boxes mounted on the outside of our coop, with the chicken entrance opening to the inside, about 2-3ft off the floor. The unit has a sloped roof we open to gather eggs from the outside. Each box is about 16" square and angled from 14-16 inches tall to allow for rain to run off the shingles properly. The hens can easily maneuver around in the boxes and can stand up in there fairly well, though not totally erect. The hens do have a preference for the added privacy offered by "curtains". I made those from pieces of feed bags I stapled to the boxes. The one box without a curtain is rarely used. I also mounted a bar in the coop a few inches in front of the boxes to make it easier for the hens to access the them. Seems to be working out well.