Preheat the oven to 350 degrees F (175 degrees C). Place butter in a large cast-iron skillet; place in oven while preheating until melted, about 5 minutes.

Stir brown sugar into melted butter in the skillet; return to oven until bubbling, about 5 minutes.

Gently place 1 pie crust on top of brown sugar mixture, without pressing down; arrange apple slices on top of crust.

Combine white sugar, cinnamon, and flour in a bowl; sprinkle over apple slices. Place remaining 1 pie crust over apple slices; cut slits in top crust for ventilation. Seal top and bottom crusts together.

Bake in the preheated oven until top crust is lightly browned, about 45 minutes.