Cut shortening into flour, cornmeal and salt until particles are size of small peas.
Sprinkle in water, 1 tablespoon at a time, tossing with fork until all flour is moistened and pastry almost cleans side of bowl.
Gather pastry into a ball; shape into flattened round on lightly floured cloth-covered board.
Roll pastry 1 inch larger than inverted 12-inch pizza pan.
Fold pastry into quarters; place in pan.
Unfold and ease into pan, pressing firmly against bottom and side.
Trim overhanging edge of pastry 1 inch from rim of pan.
Fold and roll pastry under, even with pan; flute if desired.
Prick bottom and side thoroughly with fork.