Hmm.. well I thought I'd seen them do it with the board glued to the neck, but in this video it looks like it's temporarily attached to a block to radius. It's also been fretted before being fitted. Fretboard radiusing happens at around the 2:14 mark



This one has a different angle art about 2:25

https://youtu.be/pcJ5bZWUzUI

Perhaps I wasn't paying attention, here is a fretting vid, again looks like its temporarily attached to a block:

https://www.facebook.com/bngguitars/...0458455044091/