If you have access to castoffs at a construction site, that's the ticket! You'd be surprised what they throw away there. That's how my coop was built. Windows and door from a cabin demo. It can be all a bit challenging to work with sometimes but boy the price was right. ;-) Good luck with...
I sprouted a few flats of boss this winter myself. Chooks LOVED it. Everything is brown and covered with white around here. Feel the need to get green food into their system every couple days. Doing kale and spinach too. But pretty sure boss sprouts are a bigger hit.:lol: