We made ours out of plywood. It is an open square (four sides but no back or front) with partitions in it making four even sized boxes. It sits up against a wall for a back and has some old trim nailed on to keep the eggs from rolling out. In restrospect, I would use something that could be cleaned out more thouroughly, such as the crates, but my hens lay in these boxes every time so I guess they like them!
I used some stackable shelves but not stacked so the top is open. I noticed that most people had tops on their boxes. Should I go to plan "B" and find something with a top? My girls are 17 weeks and have not started laying yet, and we are new to this. I have noticed that they perch on the sides of the boxes creating quite a mess in the box. Maybe a top would help?
I am also going to post this question on another thread but since they free range during the day should I do something to get them to lay their eggs in the boxes?