Do you get snow? If so they’ll spend a lot of time inside the coop in the winter and you should build it big enough for them to each have ~3 sq feet each. It helps reduce them pecking each other.
Build an entryway that allows you to go into the coop without stepping directly in with the chickens. It will give you a place to store supplies and food and allows you to close the door behind yourself before entering the chicken area.
