Position an oven rack in the center of the oven and preheat to 425°F. Prepare a baking sheet by lining it with foil and lightly spraying with nonstick cooking spray, or alternatively, use parchment paper. Rinse and pat dry the squash, then slice into ¼-inch thick rounds. Lay the squash slices closely together on the baking sheet without overlapping. Lightly season each piece with garlic salt and a touch of freshly ground black pepper. Spoon a thin, even layer of grated Parmesan onto each round. Bake for 15 to 20 minutes, until the cheese is melted and has achieved a light golden-brown color. Observe closely toward the end of the baking time, and if the Parmesan browns early, remove promptly. Optionally, broil briefly at the end for enhanced crispness. Serve hot.