Preheat oven to 425°F. Place a rack in lower third of oven and line a baking sheet with foil.
Prepare filling: Mix all filling ingredients in a large bowl and let rest for 15 minutes, stirring occasionally.
Make topping: Mix flour, sugar and salt in a bowl. Using your fingers, rub in butter until mixture forms clumps. Stir in almonds.
Spoon filling into pie shell and sprinkle evenly with topping. Place pie on lined baking sheet and bake 15 minutes. Turn oven down to 350°F and bake 1 hour longer, until fruit is bubbly and topping is brown and crisp. Let cool on a wire rack for at least 20 minutes before serving.