http://www.warmoth.com/guitar/necks/anatomy.cfm?fuseaction=angled
It's a glued joint, allowing the angled peghead, and using neck blanks of standard thickness.
An alternative would be to go with a three piece neck and extra "wings" for the peghead width.
This is the arrangement now used on Ibanez guitars.
It is stronger, with less tendency to warp.
