Bring water to vigorous boil and add salt. When polenta returns to boil, pour polenta into pot in steady stream, stirring with wooden spoon. Cook, stirring continuously 5 minutes or until mixture is solid but still soft.

Pour onto oiled, 10 1/2x15 1/2" baking sheet. With wet hands or wet spatula, pat polenta into smooth, flat rectangle. Let cool about 10 minutes or until firm.