This was easier than before. I clamped the neck and drilled 1/4 in pilot holes through the back and so they left a divot in the neck heel. The neck heel was then drilled with a 13/32 drill bit for the stainless steel inserts.
Here’s the key: DO NOT install the inserts without chamfering/countersinking the opening first. You’ll risk destroying and splitting the hardwood upon entering.
Afterwards, use the driver and insert with the barrel end downwards; pushing slightly and twisting to maintain center. Check each with its alignment in the neck pocket before proceeding.
I still need to countersink the holes in the back to accommodate the locking washers. For that I think ill just use a dremel.