You might want to think about:
the size of the person or persons who will be doing the work, and adjust dimensions accordingly.
where used bedding and water will go, and try to make use of gravity and nearby compost piles or gardens.
where the water source is.
how you are going to keep things going smoothly without electricity.
where the fresh bedding is stored.
how you will be aware of predators or other trouble (proximity to windows, for example)
keeping the ducks warm enough or cool enough
avoiding blocking access needed for deliveries, maintenance & repair (oil deliveries, cable technician, etc.)
making sure duck areas are cleared of old fence and construction debris (nails, screws, glass shards, string, plastic strips, clips, coins . . . )