Peel squash and grate through the large holes of a special squash slicer or standard 4-sided metal grater. Stop grating when you get to the seeds. Or halve the squashes and remove seeds before you start grating. You should end up with a mound of matchsticks, not pulp!
Sprinkle with the salt, mix, and let stand under a cover for 1 hour. Squeeze squash and set aside