The shelves are made the same way as the other pieces. I traced the original onto cardboard, cut out the cardboard, then traced that onto plywood. I used 12mm plywood for the shelves. Once they were all cut, I clamped them together and sanded them all to match.
The shelves are held in place by the grooves cut in the spine of the stand. I'm going to let them just rest in the grooves for now, if they slip out I'll glue them in place.
After assembling, I sanded every piece, starting with 60 grit when I was forming the pieces to 100, 150 and finally 220 grit to finish it off.