My first Nic cage I built I used the panels for flooring, and put thick cardboard on that and wrapped it with carpet. LOL and Mr Hopper and Nibbles still live in that one I built 3 years ago.

I think at some lumber stores they will cut the wood for you if you pay!

Lowes dose couticy cutting for free

I believe IsabelleRobyn made her cage without power tools. She used NIC cubes to make the levels too I believe and put a soft layer of something on top? You know what you could to. I wonder if you could make the shelf out of NIC cubes and use a dowel to run through it to keep from buckling on the bottom. Then make a cushion or buy a pet bed and sew ties on the bottom of it and place it on top of NIC shelf and tie the ties around the wires on the grid to keep it from sliding off the shelf. I hope you understand what I'm trying to say. xD

Oh my goodness!  You're little Rikku looks like my Skipper a few months ago.