One thing I did when I was working on the new red one I've just finished, I used the router and thicknessing jig mentioned further back in the thread, but to get everything nice and flat for glueing, I stuck a roll of 80 grit paper to thick sheet of MDF (about 4 strips wide), then I turned the blank over and rubbed it up and down on the sand paper which flattened the whole thing evenly, I also did the same thing to the underside of the maple cap when I'd finished carving it. Both surfaces were fairly flat anyway, it was just to remove the router marks. But it works well and Ill use that "jig" in future.