Combine 1/4C flour, water and vinegar with a whisk until well blended.
Combine 3/4C flour, sugar, and salt in a bowl; cut in shortening with a pastry blender until mixture resembles coarse meal.
Add the water slurry, and toss with a fork until flour mixture is moist.
Gently press mixture into a 4" circle on heavy-duty plastic wrap; cover with add'l wrap and roll dough into a 12" circle. Freeze for 10 minutes.
Remove 1 sheet of plastic wrap; let stand for 1 minute or until dough is pliable. Fit dough, plastic-wrap side up, into a 9" pie plate or tart pan. Fold edges under or flute decoratively. Line bottom of dough with a piece of foil; arrange pie weights on foil.
Bake at 400 degrees F for 20 minutes or until edge is lightly browned. Remove pie weights and foil. Cool on a wire rack.