Rachel,
Welcome to the RPF! I am flattered that my project inspired you to join. You will find many many talented people here with projects that will inspire you.
More details:
The cardboard that I used for the pattern was like what is used on the back of a pad of paper - not that thick, but solid cardboard. The base for the cover was thicker - about two to three times as thick as the pattern.
I am using leather for the cover, which had both more stretch to fill in the pattern and is porous enough to allow the glue to hold it until it is fully set. The craft glue is sort of like thicker Elmer's white glue (PVA). I wanted something that was not too fast setting to allow for adjustments.
I used the handle end of the spoon because it was about the right width to fit into my pattern with the leather cover. Since there was no way to clamp the leather into that pattern (and I tried making a wooden block with raised lines to hold the leather into the pattern - it didn't work), I just kept rubbing the cover into the grooves in the pattern until they held. I applied glue to the front all at once and then the spine, then the back. It took maybe ten minutes of pressing the leather into the pattern to get it to stick.
I would try to find some leather - old worn or damaged jackets are a good source to experiment with.
I hope that this helps. If you have any other questions, just ask.
David
By the way - that blue one went to my daughter - Rachel.