- Bake the pie on a lower rack in your oven. This will concentrate heat on the bottom of the pie and help the crust crisp.
- Brush the bottom crust with corn syrup or a slightly beaten egg white before filling.
- Sprinkle dried bread crumbs or crushed cornflakes on the bottom crust before filling and baking
- If the recipe calls for adding the filling while it's hot, don't let the filling cool before you add it to the crust.
And be sure to look at Hot Water Pastry Step by Step for a foolproof recipe for flaky pastry.