Slab Pie:

Ingredients
For the Crusts:

5 cups all-purpose flour, divided
1/4 cup granulated sugar, divided
1 teaspoon salt, divided
2 cups (16 ounces) cold unsalted butter, cut into cubes, divided
18 to 20 tablespoons cold water, divided
For the Filling:

8 cups frozen mixed berries
2 teaspoons orange zest
1 cup granulated sugar
1/2 cup cornstarch
For Baking:

1 large egg, beaten
Sanding sugar, to taste

Gather the ingredients. Preheat the oven to 400 F.

In a large bowl, combine 2 1/2 cups of the flour, 2 tablespoons of the sugar, and 1/2 teaspoon of the salt.

Using a pastry blender, cut in 1 cup of the butter until the mixture resembles coarse crumbs. Stir in 9 tablespoons of the cold water (or as needed) with a fork just until the flour is moistened.

Roll out the dough onto a lightly floured surface into a 19x14-inch rectangle.

Place the pie pastry onto the bottom of an ungreased 15 x 10 x 1-inch baking pan, pressing firmly against bottom and sides. Chill while preparing the next steps.

In a large bowl, combine the remaining 2 1/2 cups flour, 2 tablespoons of the sugar and 1/2 teaspoon salt.

Using a pastry blender, cut in the remaining 1 cup of the butter until the mixture resembles coarse crumbs. Stir in 9 tablespoons of the cold water (or as needed) with a fork just until the flour is moistened.

Roll dough into the lightly floured surface into a 17 x 12-inch rectangle.

Cut rectangle into 12 (1 1/2-inch thick) diagonal strips with sharp knife, pizza cutter, or pastry wheel.

Make the Filling and Bake
In a medium bowl, combine the mixed berries with orange zest.

In a small bowl, stir together the sugar and cornstarch in a small bowl.

Add the sugar mixture to the berries and toss to coat.

Remove the prepared crust from the refrigerator and pour the berry filling into the crust.

Place 6 strips diagonally across filling in pie pan, 1 inch apart (use every other strip for the right length).

Place the remaining 6 strips at right angles, 1 inch apart, to the strips already in place to create a lattice. Trim the ends and fold the trimmed edge of bottom crust over the strips, building up an edge. Seal, crimp, or flute edge.

Brush the strips with the beaten egg and sprinkle with sugar. Bake 38 to 42 minutes or until crust is browned and filling is bubbly.

Cool completely on a wire rack before serving.

Enjoy!