Below is a video describing how to make a string height gauge which is useful for ensuring that the slots on the nut for the strings are even and at the correct height. Sorry in advance for the childish humour.
Note that I used a FormLabs resin based 3D printer. I expect that an extruding plastic type will work but haven't tried. If you would like me to print a set of these out for you (flat base or radiused base + tip), drop me a message and I will let you know the cost. I can also supply a complete gauge if requested.STL file for the gauge base block