Jig

The "slot" coming out at an angle was machined at the same time and to the same depth as the recess. This allows a spot for my feeler gauge when I want to refernce to the surface.

There's still some more machining to do, so the the 0.060" deep side walls are deep enough that I can use an indicator to get things lined back up again when the time comes.

I also machined a 1/16" groove all around the base of the outside wall so that the part wouldn't get caught in a not quite square corner (between the flat bottom and side walls). Bigger...