Here's what I used and what it looked like. I was lucky to have some sitting around the house and snagged it for use, though you may be able to use something similar. I know walmart sells bedding padding with basically ruffles in it that I considered before I found my stuff. It's called egg crate foam or something, I can't remember exactly, I had previously looked it up for someone. I think the link is still around in my build thread somewhere (it's not that big.
For using that or a similar material, hot glue seems to have a good hold, so long as you seal the edges up nicely.
Also, as a side note, get a build thread started and get some pictures of your progress up ASAP! There you can ask questions as your progress goes along and get feedback on your work. This prevents question threads from cluttering up the forum. alternatively, there are stickys for questions such as this, and I believe the mods would appreciate your using of them.
Omega