I have seen that very same picture your talking about....
I can tell you that on the BFP
Jem neck I have they used plastic cut outs and embeded them in resin which you can find in most home craft hobby stores...then they polished the top down to a smooth level finish even with the
fret board......
using an underscore,which means the bottom of the inlay cavity is actally wider than the top helps to keep the inlay in place.......
I dont have the answer for you about question number 2 sorry....
The techniqe is different for different types of material you are going to use in the inlay.....
Here is a website that deals with pearl inlays....
http://inlay.com/inlay/pearl/pearl-1.html
* * * * *hope this helps you........