I think they're pretty flat. Might be just a bit of detritus under the piece on the right. When I lay the straight edge across the far end, there's no gap. No gap in the middle. Just a bit of fall away in the front left quadrant. I'll be sanding and possibly carving the top anyway, so I think it won't matter.
I have this lace wood for the neck... I think I said sepele earlier, but it's lace wood. I have 2 boards like this.
I may glue the remaining 10" under it so I can have the head stock angle better than this:
The red
Hmm, no. That would be weak. The lesser angle from one board would be smarter.