This is where I put mine........
As per poultry husbandry books from decades ago.....a time when farm chickens were a profit center so they studied this stuff.....nests were to be elevated off the floor enough that a bird standing flat footed on the ground (coop floor) could not see into the nests. For some reason, when birds could see in the nest, some developed the habit of eating eggs, which of course was not a good thing. Solution was to elevate them up off the floor, which also freed up the floor area below.
If you didn't provide any nest boxes, but kept them confined inside the coop as shown above, they will lay eggs anyway, but where? Somewhere in a corner in a nest they make for themselves? Where? So the purpose of the nest box is to give them a dark, safe, secure place to hide their eggs. Nest boxes above were made of plywood, but the interiors were then stained a dark color and this is the darkest (really the only dark place) inside this coop. Some will also drape a light curtain of dark cloth over the front to make it more so.
Outside of the occasional egg that is laid on the roost at night, all eggs in this coop are left in one of these three nest boxes. The birds are allowed to roam around in a large fenced in area, but all return to the house and these nest boxes to lay. Average from the past week is running over 7 eggs per day from 9 birds.