I fabricated a little jig to hold the trailing edge wedge for countersinking. I know virtually every builder of this style trailing edge has fabricated some means of supporting the strip perpendicular to the cutting bit. I simply used two cloths pins and a small piece of trailing edge (the only scrap available) and a bit of 5 minute epoxy to make my jig. I worked great.
The only scrap wood I had lying around was cloths pins..who even uses cloths pins anymore?
The small wedge is glued to the board and supports the trailing edge level