New to Chickens - Chicken Coop Design

I am brand new to chickens, but i have 10 acres and want a small amount of chickens/ducks. Maybe 8 to 10 in total.

I have left over steel from building a shed, and want to make use of it for the coop. I have heap of 75mm x 50mm RHS gal steel in long lengths. House steel frame studs, noggins and batons. And a heap of colourbond orb sheeting. I even have some galvanized mesh. Is there a smaller design I can make that will make good use of this?

My neighbors have a coop about 4meters square and 2.4m high, and it looks huge and horribly out of place, so I want something small. I am even thinking something that the whole front and back opens like on a big hinge and i can hose it out, and I never actually 'go inside'. But still somehow get eggs. Does this exist?

My plan is they are only in there at night, in the day they can roam the paddock, and hopefully dont get attacked. Speaking of which, can you train them to come home when they hear a certain sound? like if I see a fox, I can plan the sound and they come home?