Preheat the oven to 425 degrees F.
Wash, peel, and core apples. Cut thin slices of apples and set aside.
Place a saucepan over medium heat and melt butter in it.
Add flour to the melted butter and stir to form a paste. Cook for about 1 to 2 minutes.
Add white and brown sugar and water to the melted butter and flour mixture. Bring it to a boil and reduce the heat to low. Simmer the sauce for 3 to 5 minutes. Remove the sauce from the heat.
Take your crust pastry dough (store-bought or self-made). Press one rolled-out dough into the bottom of a 9-inch pie pan, covering the sides.
Roll out the remaining pastry dough larger than the size of the pie pan. It should overhang the pie pan by about 1/2 inch. Cut this rolled-out pastry dough into eight strips of 1-inch width.
Place sliced apples piled one on another into the bottom crust. Don’t worry about creating a mound as the apples shrink in the oven.
Place four pastry strips vertically and evenly spaced over the apples. Use longer strips in the center and shorter strips at the edges.
Fold the first and third strips of the pastry all the way back. Place one unused strip perpendicularly over the second and fourth strips. Roll back the first and third strips into their original position.
Now roll the second and fourth vertical strips backward. Place one of the unused strips perpendicularly over the top, just like done above. Unfold the second and fourth strips into their original position.
Repeat the steps for the 6th and 7th strips and weave in the last two strips of pastry. Fold or trim excess dough at the edges, and pinch to secure the edges.
Slowly pour the prepared sauce over the lattice crust. Make sure the sauce seeps under the lattice and reaches the sliced apples. Brush some sauce onto the lattice, too.
Bake the apple pie in the preheated oven for 15 minutes. Reduce the temperature to 350 degrees F. Continue baking until the apples are soft for 35 to 45 minutes.