I've tried several "official" nesting box designs, and neither my first single-hen nor my four newest pullets (19 wks) have had any interest in them!  The first hen chose her spot on the coop floor but liked it when I took some coco-liner (the kind used in hanging planters) and fluffed it up as bedding.  It kept the egg safe and snug and was easy to pull off any dirty parts each day. (Big Lots and Family Dollar type stores sell the coco-liner a LOT cheaper than garden-supply places, by the way!)  The new hens prefer to lay in their "bathing-dirt" pots, thank you very much!  (I have several large plastic potters left over from plant purchases which I filled with clean/dry/fine dirt, much to their bathing delight----unfortunately they find them equally delightful for laying!)  I tried just about everything to convince them to shift where they lay, but in the end I just put two of those pots into their coop's nesting area, and they found the compromise agreeable.  I did attempt to sneak some coco-liner on top of the dirt, thinking it might be a bit cleaner.  But the next morning that stuff was all over the place---except in the pot!!!  In the end, I have to admit it's not a bad nest at all.  The dirt is quite soft and fluffy, no moisture to harbor dangerous bacteria (etc), the eggs are safe from trampling....and they actually come out exceptionally clean!  I guess mother-hen(s) know best!