To each their own but I never saw the need to sand corian before gluing. Corian is pretty flat and very smooth and I don't sand it before gluing the pieces together.
If you're concerned about the CA not sticking to a smooth surface, think again, it sticks and sticks fast!
You might try an experiment by cutting up a few squares then sand half and don't sand the other half then glue them up, shuffle them around then see if you can tell which is which.