After I have the neck block holes drilled and countersunk, I can hold the neck back in position on the body and mark the hole locations on the heel by simply sticking a pencil into the holes and rotating it to get a good mark on the heel. Drilling 3/8" holes in the heel, I can simply screw in standard hardware brass thread inserts which will receive the 1/4-20 machine screws to bolt on the neck:
These inserts have very sharp wood threads on the outside and simply screw in with a screwdriver. I coat the threads with cyanoacrylate glue to soak into the end grain and make the inserts even that much more solid.
With the neck back on, here's the final look from the inside:
A this point I can leave the inside alone (like Breedlove) or I can cover the holes with tightly fitted mahogany plugs (like Collings) or a label (like Taylor.)
Whichever choice I make, the final product has a very neat look inside. The outside will also look nearly the same if I do just a little finish touchup after fitting the neck angle.
Best of all, the neck is now removable in a conventional manner and I don't have to worry about the impossible neck reset on this fine guitar!