Part 1 covers the measuring and cutting the curved truss channel.
I start these necks with 3-1/4″ x 3-1/4″ maple blanks that I get at a local mill. They are usually $20 for figured maple, and I usually get three necks from each blank (barring surprises when I cut into the wood).
I a try to get quarter-sawn wood whenever possible, especially with figured maple, which although hard, has a tendency to warp.
Guitar building is all about centerlines. I have the centerlines marked on the MDF template. Next I have to place the template on the blank with the centerlines on each end equidistant from the top edge of the blank, then mark the outline of the template:
The two vertical lines marked on the blank are for the truss rod channel. These lines mark where the filler strip (walnut skunk-stripe) will begin and end.
On most guitar necks, the truss rod channel is routed from the fingerboard side, then covered by the fingerboard. On a one-piece neck, that would be impossible, so the channel has to be routed from the back of the neck (where you palm rests), and filled with a strip of wood (in the case of fender-style guitars, this strip is walnut). The challenge is exacerbated somewhat by the need for the truss channel to be curved (deeper at the ends than at the center) so that the truss rod can function properly. Here is the jig that I made to route the truss rod channel.
The jig is then attached with 5 screws, through the jig, through the neck blank, and into the work table (this prevents movement when the router guide pulls against the ledge).
Then routed with a 1/4″ strait-cut bit:
Here is the finished truss rod channel: