On a new Graph Tech nut, it's recommended that you sand the bottom of the nut to compensate for the height rather than carve the guitar. You can then fine tune the height of each string, if necessary, with nut files or, in a pinch, a piece of 400 grit sandpaper folded as sharply as possible. After restringing, press down each string in turn on the 3rd fret. Now check the clearance of the string above the first. If it's touching the first fret, the nut slot is too low. Proper nut slot height is just a paper thickness between the string and the first fret on the plain strings and about twice that on the wound strings.