Tuner holes drilled from the back, ~3/4 of the headstock deep. These are then revealed when the headstock is taken to its correct depth.
With no bandsaw or planer, I used the same “saw dust maker” as used for the body to reduce the headstock thickness by about half. I improved my methods to get a far flatter result this time. I covered the workbench with a large sheet of MDF to give a flat consistent surface and tried to keep the neck as flat to the table as possible.
Slope roughly cut with a hacksaw, much sanding to follow to tidy up.