This is an interesting thread as it really highlights some of the more critical aspects of guitar making. Some are preferences, some or just good wisdom, and some are results of the tools used. In my process, the fret board slots are cut first because I'm using a table saw sled with a Stewmac blade and pin template. It's true that I do go back and deepen the outsides of the slots to match the radius, but it's really a minor process and I know the slots are all parallel and accurate. In the end, it's could very well be slower than doing them by hand.