I used the track saw to make the straight cuts in the walnut (and also a jig saw for the part that was too small for the track saw), then flipped it upside down, traced it out, cut it the tiniest hair oversized, then started shaving it with a block plane and sanding it as necessary. It took a couple hours, but it was faster than I think I was expecting.
I have always been afraid of doing something like that and getting half way through and finding I have taken too much off. Maybe I will try it sometime.