Make the Pie Crust: In a large bowl, whisk together 3 cups flour, 2 tbsp granulated sugar, and salt. Cut in 1 cup of cold, cubed butter until mixture resembles coarse crumbs. Drizzle in 6 tbsp of ice water, tossing with a fork until dough comes together. Add more water, 1 tsp at a time, if needed.

Press Crust into Pan: Divide dough, two-thirds for the bottom and one-third for the top. Press the larger portion evenly into the bottom and up the sides of a 10x15-inch jelly roll pan. Chill in the refrigerator.

Prepare Apple Filling: In a very large bowl, toss sliced apples with lemon juice. In a separate bowl, whisk 3/4 cup brown sugar, 3 tbsp flour, cinnamon, nutmeg, and allspice. Sprinkle over apples and toss to coat. Drizzle with 2 tbsp melted butter and toss again.

Assemble Pie: Pour the apple filling into the chilled crust and spread evenly. Crumble the remaining one-third of dough over the top of the filling.

Make Crumb Topping: In a medium bowl, combine 3/4 cup flour, 1/2 cup brown sugar, 1/4 cup granulated sugar, and 1/2 tsp cinnamon. Pour in 1/2 cup melted butter and stir with a fork until large crumbs form. Sprinkle evenly over the pie.

Bake: Bake at 375°F (190°C) for 45-55 minutes, until the crust is golden brown and the filling is bubbly. Cover edges with foil if they brown too quickly.

Cool: Let the pie cool completely in the pan on a wire rack for at least 2-3 hours before slicing and serving. This allows the filling to set properly.