Essentially, I laid a tarp, put the construction plastic over it and put the dog pen in the middle. Then I folded the plastic and tarp up about 10" and clipped it with clothespins. I used clothespins to put the bird net over the top (the inexpensive plastic netting like you put over bushes). It was easy to undo an end to change food and water. I could also clean by dropping the net in the center so the birds were on one side while I changed the bedding and then repeating for the other side.I see. So you put the plastic on the outside of the cage?
I like that plan.