Hi Chinjazz!
well, there is not any secret on this... will try to explain as best as my english can as my natural leguage is spanish.... so:
The most beauty of singlecut basses is the heal carving, full access to all frets, very soft transition between body and neck, and your right hand should slide all the neck as any other bass, with no stops or funny shapes when the neck meets the body at 12th fret.
i really like to build my single cuts as a SET NECKS, as i feel and hear they sound better than neck-tru, so the most important thing on this is to get the best fit on the "neck pocket" before glue... for this, i really like to leave 4" longer the neck from the last fret or where the fretboard finish.... as this join will meet very close the neck pickup; so, to get a nice fit pocket, i place the neck with fretboard glued and sloted over the body, an well centered, BUT i draw my lines with the 11 position at the end of the single cut horn; then i place some MDF boards with double side stick tape right next to the neck, bouth sides and end. i cut the neck pocket with my router and nice Amana bits with ball at desided deep. once done, the neck will not be as tight as i wish, so i slide the neck to get the 12th fret place where the end of the single cut meets, so i will have a very very tight join. if everything looks fine and the neck can hold the body weight im ready to glue..... just 3 clams are needed, 2 for vertical and one to get the side of the neck joined to the single cut.
the carving is just a lot of work that i do with chiesels and sand.... let me see i can post a link with my facebook page where i have some videos doing this....