The number of boxes to hens is not set in stone, but typically hens will lay eggs where others lay their eggs. They will develop their favorites boxes and leave others empty. If you have laying age hens, the young ones will start laying in the same place once they are old enough. If you have no other laying age hens, then once yours get old enough to lay, you can put plastic Easter eggs in the box to give them the hint. When starting with young chicks that still sleep in a pile to keep warm, block the boxes off until they are close to laying eggs. That way they will get in the habit of sleeping on the roost when they grow a little bigger instead of sleeping in the nest boxes. (Roost should be higher up than the nest box).
They prefer privacy for laying eggs. Some people make a curtain over the entrance to keep it a little more dim in the box. I cut a section off an empty feed bag, cut strips in it and stapled it over the entrance to the box. Gives them more privacy. When they get close to laying, I stop letting them free range for a while. You want them in the coop and run so they will get in the habit of laying in the boxes and not under a bush, in the garden or under a porch where you can't get the eggs.
