I don't have any work-in-progress shots, so I'll first describe what I did and then show you the end result.
klik had set aside some yellow and red ones, so I used those to create a mosaic on a piece of board. Then I cut out a 'window' in another piece of board so that it would fit on top of the mosaic'ed board. I trimmed the top board so that it was 2.5 mm smaller on all sides.
Then I selected a nice piece of paper from our stocks: the reds and oranges fit nicely with the ash leaves, so it turned into an autumn book cover... I marked the window for the mosaic, cut that out and folded the paper through the window -- so that the sides of the window were covered in paper as well. Next, I glued the two boards on top of each other, and folded the paper around the second board.
Because the top board is smaller than the bottom board, you get a 'rounded' effect on the cover, which I find quite attractive.
The end result.
The mosaic. The lighting doesn't do the colors justice.
Close-up of the rounded edges of the resulting board.
I learned a lot about precision cutting, and it's such a cool effect that I think we'll be using this technique more often from now on.