Below, I have drilled the holes for the mounting posts. They are drilled to a depth of the bushing height + 4 mm since I intend to route the recess to a depth of 4 mm. I drill them before routing the recess in order to have a flat surface with my taped guide marks still on it to drill on.
Next, I used the mounting post holes as reference points for the recess.
The next installment will cover how I route the clearance for fingers to tune, below the tuner knobs. The jury is still out on how to achieve this in the best and most aesthetically pleasing way.