Here is a glimpse into my assembly process of the book covers. I posted a shot of this one in progress awhile back (here, if you forget). So far, I've been cutting wood pieces from a large piece of painted orange plywood that I used as a desk a few years ago. I have almost cut up the whole thing, so soon I will have to hunt through my wood pile to see if I have more plywood of a similar quality and thickness for future covers. (This wood is very solid and not prone to warping, like some other cheaper, lighter-weight wood pieces you see at Home Depot. But it also takes longer to saw through...)
After sawing, which is probably my least favorite task, I sand down the edges and decide what color to paint it (unless I keep the orange color). I decided to paint this one more of a red-orange, to match the edge of this particular book cover.
After painting the wood, I put a protective finish over the sides and the back. Then, I use this glue to adhere the book cover to the wood - this glue can pretty much be used to adhere anything and make a strong bond.
Finally, I hammer nails in each corner and put some kind of hook or wire on the back. (Originally I had planned to attach the book covers with the nails alone, but even though they're not really necessary since I use the glue now, I still like how they look). And it is done!