If you are able to obtain palates, remove the boards off one side of it, use 2 wide for the back, attach to 2 more palates secured together as the floor (take under side of floor wood off and set on rocks), use wood you have removed to fill in the back to make a wall, then if you like, you can use 2 more palates as the other side, cover that will a heavy gauge wire and cover with a heavy clear plastic that you can pick up at most
Walmart stores.
The ends would probably take 1 palate each and one 4x8 (I think) sheet plywood for the floor. Now as for a door, you can make one with the frame work of the palate or a lift cover. I'd cut some strong small trees as rafters and place scrap wood over it, cover with a tarp staple down and you will be surprised how much you can accomplish. Palates are free, go to your local
Walmart store and ask about it. With 4 chicks, using a few sized trees (2 -4 inch) size, for roosts.
Sit down with what you have, do an inventory and go one step at a time, mark down what piece you wish to use for what, that way you won't use things in the wrong place.
Do not get overwhelmed, also, what is wrong with a dog house for a coop! That is where I began, cover the outside with plastic, roof the whole pen and you have a beautiful home for your birds! Chickens are tough if you just keep the wind or breeze from them! The clear plastic will allow sun in and shield them.
Good luck and sorry its so long!