Thanks guys.
Floor--it sits in our dairy barn backroom, so the floor is cement. I put sawdust down first, about 3 inches for insulation, then newspapers, then paper towels. I was going to leave it but decided to put in two big towels.. they don't slips on it, they can't lift it up and it's washable.
The side connections. On the end we screwed on a piece of board, maybe 1/4 inch by 2 inches wide. Then brought the other end and overlapped it, and pushed it through on the screw, then a bolt. I will take a close up picture so it's more clear. The whole thing took about 30 minutes to put together.
When we are done, we just unscrew the sides and put the flat pieces of plastic up against a wall. It is waterproof so we can wash it off.
It is about 5 feet in diameter and about 18 square feet.
I think maybe for the next batch of ducklings we will make a screen floor, you know maybe two inches high with lots of 'beams' maybe every 6 inches. It would be much easier to just have them on wire than on the towels. Definitely cleaner!