We built this based on the Wichita Cabin plans - the base is about 5 x 10. I prepainted all the wood and just touched up whatever needed it after it was put together. We used polycarbonate roof panels without anything underneath because we don't have a lot of wind here and it's very temperate all year long. I used boot trays as poop boards, but if I do this again, I'd use shallow plastic bins (more rigid and easier to remove to clean).
In an effort to respect the intellectual property rights of the original designer of the plan, I am purposely not providing detailed build instructions in my article. It's meant to show another Wichita Coop built and how it turned out. Plans were purchased from here: