Fire the glass squares up to 1500 degrees Fahrenheit and hold for 8-10 minutes.
In a small kiln (like my Caldera), I go AFAP (as fast as possible) to 1500 and hold for 10 minutes, then the next segment of the firing schedule is off. The kiln holds enough heat, and they are small enough that I'm not worried about thermal shock. Plus, I'll be firing these again in a larger project. They'll really anneal in that piece.