Very easy to put together. Make sure it’s on level ground so the door opens and closes easily. I personally don’t think it’s big enough for 12 chickens. Maybe 6. I have 4 mature hens and they have plenty of room, but I wouldn’t think of adding anymore if you want them to have space to walk around. I’ve also added a dog playpen to the side of the coop with the door so they have a huge open run when I’m sitting outside with them. Will be buying another when we add pullets to our flock of 4 hens!!!