I was going to flip some milk crates on there sides but after looking at your bucket 'O' hens I might just grab a bunch of buckets (for free from work) and save myself the trouble of stealing the milk crates. Nice job.
We use 18 gal totes for everything, and my hubby, made our nest box out of those. In one pen he cut a square hole on the short end and then wired it to the out side of the pen so that we could check the nest with out going into the pen itself. In another pen he placed the tote or tub which ever ya'll want to call them, inside the pen, and cut 2 small square holes in the longer side of the tote, and then put a wire seperator inthe middle of the tub to make 2 nests, and then use a peice of wire to hold up the doors to the nests, so that when we get a broody hen we can shut the door so she will have her privacy.
We have also got a hooded cat litter box for a nest box, stacked buckets, and old srcape radio cover and an old washing machine shell, for nest boxs.
I find they will lay in about anything as long as it is an enclosed space.
I will post pics later.