The coolest nests i've seen are the ones somebody made out of those 5 gallon jugs of oil for cooking.  They're kinda square and they cut our an area in the side of the jug, but in bedding and bam. You have a nest box.  My chickens would love it.  I just keep forgetting to go around and ask for the jugs.  I used a small carrier once because my AO didn't want to lay her eggs on the shelf where the others do.  So I gave her a crate.  Then the others started using it and she quit.  I have even seen people use litter boxes. The ones with the top.  Five gallon buckets turned on their side.  Small storage containers, without the lids of course.