we built quite a large flight cage for my birds, just this past summer. I envisioned it to be large, but when we were finished it was HUGE. It stands almost 7 feet tall, from floor to ceiling, and is divided into 4 large sections....you probably don't want yours that large, but each section is a good size. 2.5ftx2.5ftx3ft high.
we used non-treated wood, hardware cloth, and about a zillion screws, lol.
each section has it's own wide door,on hinges, with a slide lock.
I place newspaper down on the bottom in each section, as there are no trays...and it works fine, also has castors on the bottom to move this monster!
my nephew who is 17, built this for me, which was his first big project and did a great job.
my birds love the room to fly around, and it's fairly easy to clean.
although some people may not want to use wood as it can harbour bacteria, mold, mites, etc...if not kept clean. I spray mine with A.I.L. every 3 months or so for prevention, and is not that hard to clean, a vacuum does wonders

1st pic:my nephew is almost 6 ft tall, and is just getting the first door on
2nd pic: completed and in my bird room...sorry for the picture, I but it was so big I could not fit it entirely into the camera lens.