Lightly coat a 9x9-inch baking pan with cooking spray; set aside. For pastry: In medium bowl, stir together unbleached flour, oat flour and salt. Using pastry blender, cut in the 1/4 cup butter or margarine until pieces are pea-size. Sprinkle 1 tablespoon of the cold water over part of the flour mixture; gently toss with a fork to mix. Push moistened pastry to side of bowl. Repeat moistening flour mixture, using 1 tablespoon of water at a time, until all of the flour mixture is moistened. Form dough into a ball.