We set up a tall folding dog kennel 4x4 and 3-feet tall sitting on a thick plastic sheet taped to the floor/rug with wide blue painter's tape (12 months later that stuff is STILL in place!). We line the top of the plastic sheet with our old Wall Street Journals and every day just roll up the spilled feed and poops. We don't use any slick colored newspaper sheets.
Anyway the pen is portable with no floor and no top - the 8 kennel panels can be configured in any shape like octagon, square, or rectangle and more panels can be bought individually to make it bigger - Walmart had the best prices on these collapsible kennel walls that fold flat and out of the way with no top or botton panels to deal with. Ours is 3 feet tall (they also come in shorter or taller heights) with an access gate in one of the panels so we can get into the pen. Silkies can't fly so having a roof on the kennel was never a need and not having a roof means we can stand in the cage during daily cleanup.
This kennel was what we used when we had to quarantine juveniles before introducing them to the main flock. Today we use it as an isolation pen or hospital pen for sick or recuperating birds. For LF we clip a bird net to the top of the kennel to keep them from flying out. The 4x4 kennel dimensions would make a nice nursery for chicks if a smaller guage wire border were fastened around the perimeter base as a chick barrier. We put a portable perch in it and a nestbox. In fact one of our Silkies comes into the house to lay her egg in the pen and goes back outside again. Silly but my DH is a softie and lets her.
P.S. If we have a lone bird recuperating in the hospital pen and we leave for the day we leave the radio on a talk show so the bird can hear voices and not feel alone. They seem to like radios and if at their level they push each other to stand in front of the speakers.