In a medium mixing bowl, combine the 1 cup flour and salt; add shortening. Beat with an electric mixer on low speed until pieces are the size of small peas. Add the cold water; beat on low speed just until dough begins to form (about 15 to 20 seconds). Form pastry into a ball with hands; gently flatten. On a lightly floured surface, roll pastry into an 8-1/2x8-1/2-inch square. Cut several slits in pastry. Set aside.
In a small bowl, combine the 3/4 cup sugar and 1/4 cup flour. Place blackberries and almond extract in a 2-quart square baking dish. Sprinkle sugar mixture over blackberries; toss to coat. Dot butter pieces over blackberries. Place pastry on blackberries. Sprinkle the 1 tablespoon sugar over pastry.
Bake in a 375 degree F oven for 45 to 50 minutes or until blackberry filling is bubbly and pastry is golden. Cool slightly on a wire rack. Serve warm. Makes 6 servings.