Thanks for your reply Ben!
So why wouldn't you tap it from the side (as in b above),
seems more logical to me as there could follow some wood with the nut as it is glued
to the fretbord side of the slot.
Might happen if the glue joint is stronger then the wood itself.
To me it seems more likely to do so in the a) alternative.
Of course im no expert, that's why I'm asking