I cut my own layers out using Feye's method and my collarbone as a guide.
First, sitting my fingers on top of my collarbone when it was shorter and then
placing them underneath the collarbones as it grew.

I stayed there until I cut all the layers out.
Plus, it's a flattering length for shorter hair.

You could also use a tape measure and with your hair parted in two and pulled to the front, find a point on your face or head and measure down from there.
Repeat on the other side.

You can do it yourself and you will have complete control.