Line 9-inch pie plate with pastry.
Mix the flour, sugar and salt.
Sift 1/4 of this mixture over pastry; fill with berries and sift remainder of sugar mixture over fruit.
Dot with butter and cover with upper crust.
Bake in hot oven (450) for 15 minutes; reduce heat to 350 and bake for 30 minutes more, or until crust is delicately browned.