Sift flour and salt into a bowl. Using a pastry blender, cut in 2/3 of the shortening until the mixture resembles very fine crumbs. Cut in the remaining shortening coarsely. Do not overwork. Sprinkle with cold water, and stir with a fork until it clumps together, adding more water if necessary. Squeeze into a ball, then roll out on a floured board. Transfer to a 9-inch pie plate.