I use cardboard boxes as nesting boxes, I figure they will have a short life but I can shred them and use them as bedding or brown compost and replace them cheap. I use a wooden frame I built from scrap wood that someone illegally dumped somewhere here in the city. Sounds a lot easier than it is though, The framing has to match the boxes and hold them in place. I bought some expensive boxes too.. from Uhaul. I wanted to make sure I could buy the exact same size in the future since I do not want to readjust the framing. Some uhaul places allow people to return used boxes so others can use them for free but the one local to me does not do that so I paid for new ones.
I am building a coop right now that will also act as a straw storage building and I figure I could stagger the stacked straw and make cubby holes that chickens could use as nesting areas.