I love this method of brooding and integrating! I used a similar method with my tiny brood of 3 chicks. It's amazing how those little birdies at only 4 or 5 weeks old are just naturally running around and roosting safely with the big girls so quickly and peacefully.
I like the use of cardboard in this setup - easy to source, alter, replace as needed. As the chicks grow it's simple to just make the panic door holes larger. And because of the L shape of the brooding area, hens can't just put their heads in and get to the chick feed.
