i am following the gore / gilet "bolt-on bolt-off" neck construction. this consists of the neck tenon and receiving mortise in the body, and another tenon attached to the neck that has another mortise in the body. the upper tenon sits flush with the top of the guitar. there will be two bolts through each mortise and tenon attaching the neck to the body. there are several reason given for this construction - these include: a removable neck obviates difficulties with a neck reset down the road, because the upper tenon is attached to and supports the freboard across the body joint it helps the neck and upper bout to stay in the same plane, which also allows fretting of the fretboard prior to attaching to the neck (and hopefully eliminates the need to level and recrown and polish the frets later in the finishing process), and also generally facilitates easier finishing.

shown here is the jig for cutting the upper mortise. it indexes off of the truss rod slot in the neck. note the patched bit in bottom of the rectanglular cutout - this part of the mortise will need to precisely line up with the upper transverse brace which was earlier drilled with a hole to access the truss rod. luckily i measured twice even after initially making the jig.