All the time in the world, and still not enough to get back to this. Until today...
A lot of people buy a nut ready cut. Here is how I was taught, using a bone blank
Sand a pencil in half
Slide it across the frets to mark the height of the "zero fret"
Then sand the blank to follow the radius, at an angle matching the headstock break angle, to a mm or two above the line on the fretboard side
Mark out and cut the slots. Not quite fully to depth yet - that's for final fettling
Then sand it nice and smooth
I've still got a few grits to go through yet, but then I can string it up and start fine-tuning the slot depths as I set it up