Achieving a crisp, golden bottom crust without over-browning the top or leaving the filling undercooked comes down to managing heat distribution throughout the bake.
To begin, position your oven rack on the lower-third shelf and place a heavy baking sheet or baking stone on it while preheating the oven to 425 degrees Fahrenheit (218 degrees Celsius). Placing the pie directly on the preheated metal sheet delivers intense, direct bottom heat right away. This quickly sets the fat layers in the pastry dough, crisping the base and preventing the bottom from turning soggy or staying raw.
Bake the pie at this initial high heat of 425 degrees Fahrenheit for the first 15 to 20 minutes. Afterward, reduce the oven temperature to 350 degrees Fahrenheit (175 degrees Celsius) for fruit and custard pies, or 375 degrees Fahrenheit (190 degrees Celsius) for dense fruit fillings, and keep the pie on the lower-third rack. This gentler heat gives the interior filling sufficient time to simmer and thicken without scorching the exterior pastry.
Around the 25 to 30 minute mark, check the outer crimped edges. If they have reached a pleasant golden brown, gently cover the perimeter with a pie shield or a ring of aluminum foil to insulate the edges from direct radiant heat. Continue baking until you see the filling actively bubbling in the center, which confirms that any starches or thickeners have reached their activation temperature and the pie is thoroughly cooked through.