Thanks, Steve. For some reason it only took one pass on the first side but three more on the other. I must have had the router set a little deeper for the first side. Clamp it in, clamp it flat to the bottom with long reach vice grips, hot glue for two inches along the edges in three places to hold it from lifting up (vice grips off again), rout it, pry it loose and clean the glue off. Total time for both sides, maybe an hour or so. With a wider router bit I could have done it faster but I only had a 1/2" diameter one that would reach down far enough to do the job.
Another half an hour to clean up afterwards.
The apron works good. I make a mean taco filling, too.