So, after you’ve got the neck foot shaped, you get to do the hard part. The neck set.
You start off by drawing the profile on the violin’s ribs a bit smaller than the final size. There’s some measuring and math involved, but I won’t bore you with that.
After you’ve got everything drawn on, you score the lines, cut into the edge of the top plate a little inside them, and cut out some notches. Those notches will act as your buffer zone while you carve out the rest of the top plate in between them.
The next step is to take a chisel and start shaving off wood. You’ve got to take it really fine, otherwise you risk detaching the ribs from the top block, and every time you take some wood out, you need to re-score the lines or else you’ll have the wood chip out on you. For the first bit, you just keep everything nice and square, and keep removing wood until you’ve gone all the way through the purfling.
This is where things start to get really hard. When setting the neck, you have to precisely control the centering, length, pitch, yaw, and roll of the neck. Your manipulations of the dovetail change all of that. The bed controls the depth, pitch, and yaw, and the sides control the roll and centering. Fortunately, you get to do the bed and then the sides, so long as you’ve taken proper care setting everything up.
You control the depth by making the whole dovetail deeper. You control the pitch by angling it back—the back end is deeper than the front. You control the yaw by making one side deeper than the other. Changing any one of these things affects all of the others, so you can’t just concentrate on getting one right and then doing the others.
You start out with the chisel and scoring method until you get close (the rule of thumb is that you’re always closer than you think, so leave lots of room for error), and then move on to sanding blocks for precision control. Even then, it’s easy to mess up. A few swipes in the wrong place, and all of a sudden the end of your fingerboard has dropped half a millimeter, or swung to one side.
Of course, the entire time you’re doing this, you’re also religiously checking that the neck is doing what you want—placing it in the groove and measuring each variable.
When all that is done, you’ll hopefully have your neck bed properly established and you can move onto getting the sides done. If you screw up, you get to shim it and start over.