Necks are bought in rough sawed form, often slightly warped from drying. The first step is to carefully true and square the blank on all sides with a long plane (same as when jointing plates). Next a slice is cut from the edge, in order to check for internal stresses. If the slice warps, the neck has stress built in and I might discard it, or opt for reinforcements (rosewood or carbon fiber). Reinforcements are also added when the wood is too low density. This one is quite heavy, just like mahogany, and stable, so no inserts are going to be used. Third step is to do the cut for the headstock scarf joint. Fourth, the cut faces are trued again with the plane, and the endgrain face is sealed with hide glue. When dry, it is planed again and then the two pieces glued together. The resulting headstock face is again sealed with glue, and then again planed, and then the headplate and veneer sandwich is glued to it.