Mine are home made wooden rows (of boxes) and are square maybe just over a foot wide (not sure how deep but a few birds can sleep in one box). They are bedded with sawdust (nice and thick). Ohh and there is a lip on the bottom of the boxes to prevent eggs from falling out, and keeping sawdust in. The nesting box rows are lined down both sides of the coop, 2 rows each side (one row stacked on another) with wooden perch's balanced across the boxes.
Ohh its worth noting that the wood is non-treated as some wood that is treated (and some paints) have components that cause the chickens to become ill and can even kill them.
Good'Luck