Hi! Unfortunately our ducks died almost two weeks ago unexpectedly from an unknown cause. We have some guesses, but who knows?
Anyways we locked our ducks up in the coop at night and let them free range in the day. This depends on where you live though. On one side of the coop was a hen door and on the opposite side was a window, in the front were the big doors. On the back side of the coop was a small ventilation hole covered in hardware cloth. The window was also covered in hardware cloth. The coop was 4x4 (8 square feet) or maybe a bit bigger. There was a roosting pole in there from when we had guineas but that is optional. The whole inside of the coop was painted in this white paint (I'm not sure exactly what it was but I will do some digging and hopefully find out) this helped when we hosed the coop out every once and a while and cleaning the poop off the walls and floors. Here is a picture of the coop (it's a bit blurry because it was raining).
Hopefully this helps!