If you are only building one guitar (good luck with that plan!!) or you are smart, you should probably buy one of the Pitbull pre-cut nuts. But if you intend doing more that one guitar and are a bit of a masochist like me, you’ll have a go at doing your own.
At this stage it is important to point out that if you want a good result unfortunately you will probably need a set of fret files. It is possible to do it without the proper files, but not recommended.
A Google search will show up a hundred different ways of doing nuts, so mine is probably not the best, but it works for me.
First off measure the height of your frets. Easy…... straight edge across 2 frets, and a feeler gauge to measure.
Then, with the nut in place, mark the fret height on it. A feeler gauge can be easily coaxed to bend to the radius of the neck by applying a wee bit of pressure on either end of the gauge.
The nut with a pencil line showing the approx height of the frets.
String spacing. It is important to get this right. There are plenty of calculations on the net, or buy a string spacing gauge. I use a simple layout plan that I downloaded off the net when I did my first nut. It has compensated string spacing (to take account of the different string gauges) and I have never felt the need to use anything more sophisticated, or expensive.
Then into the hobby vice, out with files, sandpaper and nut files and file away until you are close to (but obviously not below) the line.