Nesting boxes are not as simple as most people think. They depend upon your purpose, or purposes for the hens to lay in. Do you plan on free ranging? Do you plan on letting them sit and hatch chicks. Either way, I take into consideration what hens naturally like as nesting place, and the material. For starters, hens like a hiding spot. So, I always shread an old tarp and tac it over the opening. Most people use pine shavings for the nesting material. However, fine stem grass hay is a more natural nesting material that they choose themselves when making nests out under things. Then if you're going to let them sit and hatch chicks, the placement of the nest is very important. When chicks hatch, they can't fly out of these nest boxes that people put up of the ground. Therefore, I'd put the next box on the ground, so the chicks can get in and with their mother.
If you plan on free ranging, I'd make the nests as I described. If not, your hens will stop laying in the nests you created, and fine themselves another place to lay. If you start suspecting that they're laying elsewhere, then keep them penned a few days. That will reaquaint them to have to use the nests in the henhouse. Then they should continue to use them. I've had it be a back and forth with one of my game hens. She just has that wild nature.