Hi Veronica - I would suggest hay in boxes and have a ladder leading up to box so that they don't have to fly up to box. Finally, is there an edge or lip on the nest boxes?
Funny but true story. We just moved to a new home (actually old plantation home) and it had the old original coop. Nest boxes were just open boxes nailed to wall - no lip or edge on front of box. Looked like eggs would just roll out. So, I added a board about 1 1/2 inches high to front of boxes. I wanted to be sure they knew these were their new nest boxes so I put a store bought white egg in one box. I came out later to check and see if anyone had laid an egg and found the white egg missing - no sign of it at all. I'm thinking "oh no, we have some kind of egg-stealing predator here" but I couldn't find any sign of what had stolen the egg. Later that day one of my girls laid an egg in box. A little later I found it on the floor, unbroken, and put it back in box. Same thing happened again. Finally stuck around to watch. One hen would lay her egg and leave. Next hen would come along and promptly roll it out of box onto floor, 2-3 feet below, and lay her own egg in box. Next one did same thing. Finally added a half-front to boxes so they can't roll each other's eggs out. There are 8 boxes but they will all lay in whichever box the first hen lays in that day.
The mystery of what happend to the store bought egg - as best I can figure out - is that it was of such a thinner shell that it most likely broke when it hit the ground a few feet below. And they probably all had a nice egg breakfast and left nothing of it. However, none of the eggs that they laid and rolled out of boxes broke when hitting ground and were there for me to find later. Goes to show you what a stronger shell free-ranging chicken eggs have.
