Creating the perfect Apple Slab Pie can be straightforward if you follow these simple steps:

1. Prepare the Crust: In a large bowl, combine the flour, salt, and sugar. Add the chilled butter and mix until the mixture resembles coarse crumbs.

2. Add Ice Water: Gradually add ice water, one tablespoon at a time, mixing until the dough comes together. Divide the dough in half, shape into disks, wrap in plastic, and refrigerate for at least 30 minutes.

3. Preheat the Oven: Preheat your oven to 375°F (190°C).

4. Make the Filling: In a large bowl, toss the sliced apples with sugar, flour, cinnamon, nutmeg, and lemon juice. Set aside to allow the flavors to meld.

5. Roll Out the Crust: On a floured surface, roll out one disk of dough to fit a 12×17-inch baking sheet. Transfer the rolled dough to the baking sheet, pressing it gently into the corners.

6. Add the Filling: Pour the apple filling into the crust, spreading it evenly. Dot the mixture with small pieces of butter.

7. Roll Out the Top Crust: Roll out the second disk of dough to fit over the filling. Place it on top, pressing the edges to seal. Cut slits in the top crust for steam to escape.

8. Brush with Egg Wash: Brush the top crust with the beaten egg and sprinkle with granulated sugar.

9. Bake the Pie: Bake in the preheated oven for 45-50 minutes or until the crust is golden brown and the filling is bubbling.

10. Cool: Remove from the oven and allow the pie to cool for at least 15-20 minutes before slicing.

Following these steps will help you create a beautiful and delicious Apple Slab Pie that everyone will enjoy.