I use a dedicated miter-fence extension bar on my table saw, with a well-squared stop- block clamped to it, to facilitate the subsequent slotting steps. Note the following:
a) a saw blade that cuts a .095-inch (.24 cm) slot has been chosen. That seems to be the ideal slot size to properly accommodate a .080-.085-inch (.20 to .22 cm) side with a residual curve in it. I had to try a series of different saw blades, of varying sizes, until I found one that gave me the desired kerf.
b) the saw blade must be tilted to the right
until it is 89 degrees to the table surface. I've trimmed a piece of
scrap (shown beside the blade) to the correct incline and then aligned
the blade to it.
The workpiece is held with one hand firmly against the miter fence extension bar and the vertical stop block so the slotting cut is made right at the third line--while with the other hand, the fence and the workpiece is slid across the spinning blade, effectuating the cut. The blade extends about 1/2-inch (13mm), or just shy of the centerline at the heel-tip root.
Another view of the blade about the slot the heelblock.
After the slot is made, the workpiece is simply flopped over so now the shaft, and not the heel-tip, rests against the miter-fence extension bar. The workpiece is also pressed up to the vertical stop block as it is slid past the saw blade, completing the machined neck blank.
Another view of the final slotting cut.
The heels are ready for final hand shaping, the bulk of the waste having been removed by the saw, enabling a refined and symmetrical final product
One of those neckblanks ended up on this finished Cocobolo classic guitar