How to make a flaky pie crust?

I made an apple pie today from scratch from some of my weekend apple-picking bounty. The filling is fantastic, if I do say so myself (Northern Spys are great baking apples!), but the crust disappointed me. It came out more shortbread-y than flaky. I have more apples that I’ll want to use up soon, so when I bake another pie, what are some tips for a really flaky crust?

My recipe for a 9-inch pie with top and bottom was: 2 cups all-purpose flour, 1 teaspoon of salt, ½ cup of Crisco, ¼ cup of butter, 5 tablespoons of ice-cold water.