This is my process for laying up bookmatched veneer pairs. Once I've figured out what halves belong with the other and how I want them oriented, I used my track saw to just trim the inside edges that will be glued together ensuring straight edges to work with.
Next, I join up the pairs and tape them together tightly making sure everything is lined up. Here are a couple of pairs as examples.
Once taped up, I fold one on to the other and flip them over then set them up in an upside down "V" revealing the gap between.
Then I carefully fill this gap with glue:
Once that's done, I set them back down flat with the glue side up. Wipe off the excess, lay some wax paper down over them and apply some weight on top so that they dry flat.
Once the panels were dried, I used the box as a guide and outlined it onto the veneer. Again, I used the track saw to make the cuts for the final (rough) shape.
I was also working on the final ziricote layout.
After a couple of tries, I came to a final decision on which scraps to mate up for the second baffle. I did not have a lot of material left to work with.
Here's the small bottom panels: