In a mixing bowl, combine flour, sugar, and butter. Mix until crumbly.

Gradually add ice water, mixing until the dough holds together. Form into a disk and refrigerate for 30 minutes.

In a large bowl, combine blackberries, sugar, cornstarch, lemon juice, and cinnamon. Toss gently to coat.

Preheat the oven to 375°F (190°C). Roll out the pie crust on a floured surface to fit the pie dish.

Place the rolled crust in the pie dish and fill with the blackberry mixture.

Roll out the second crust and place it over the filling. Seal and cut slits for steam.

Bake in the preheated oven for 45 minutes or until the crust is golden brown and the filling is bubbly.

Let cool before serving to allow the filling to set.