Not all fun and games, no siree! Quite laborious with hand tools.
Anyways, here is the first stage: measuring and marking. Actually, there are preliminary stages that came before: selecting and buying the wood, getting it re-sawn at the proper thickness -- not something I can do on my really basic bandsaw -- doing the initial sanding (more of that after the fret slots are cut), so there's been a previous journey to get to this "first" stage as there is in fact for every part of the instrument.
First, admire the wood: rosewood in this instance. Get a table of the fret positions for your chosen string length from an online calculator (millimeters work better than inches). Mark those positions in pencil: I've just acquired a "stop rule" to make this process a tad easier. Then, double-check the measurements. Mark in pencil the whole length of each fret across the fretboard, double-check again, and go over that with a marking knife or blade (another new acquisition: an engineer's square). The cut made by the marking knife makes it easier for the saw to grip the wood where you want it later on.
There may be easier, more efficient methods: all suggestions gratefully accepted.