Combine rice flour, potato starch, tapioca flour and salt in medium bowl. Cut in butter with pastry blender or two knives until mixture is crumbly. Form well in center. Add egg and vinegar; stir gently with a fork until just blended. Sprinkle with water; blend together with a fork and clean hands until mixture just holds together and forms a ball. (Be careful not to add too much water as dough will be hard to roll.)
Shape dough into ball and divide in half. Cover one half with plastic wrap; set aside. Place remaining half on lightly floured (use rice flour) sheet of wax paper. Top with additional piece of wax paper. Roll out dough to 1/8-inch thickness. Remove top sheet of wax paper and invert dough into 9-inch deep-dish (4-cup volume) pie plate. Slowly peel away wax paper. Trim excess crust. Turn edge under; crimp as desired. Repeat with remaining half.