My hens didn't like the nest boxes at first (I put the box in before they were laying to get them used to it) because the masonite floor was too slick under the shavings, and the shaving would squirm around under their feet. It was also leading to the shavings being knocked out of the nests.
I stapled "Astroturf" to the floor of my nest boxes. The 'turf gives some traction to the floor of the nest and keeps the shavings in. I also used a scrap of baseboard for the front lip of the nest. It presents a narrow edge up, discouraging them from standing on it for very long. They have a low roost that they jump up to and them jump into the nests from there.
They still kick some of the shavings out, so I just toss a scoop of shavings at the nests when I top up the coop floor.