My very first coop was so small (maybe 4x2), that a nest box wasn't really practical. I just let them lay in the floor. Of course, I kept that coop spotlessly clean, so never had a problem with dirty eggs. Now I use old milk crates with a wooden board to keep the shavings in. Also have a large plastic doghouse in the run for the ducks, and the girls like to lay in that, too. Chickens are so awesome and adaptable; you can use almost anything that makes them feel safe and protected.