Step 1: Preheat your oven to 375°F (190°C). If using a store-bought pie crust, carefully unroll it and fit it into a 9-inch pie plate. Trim the edges to about a 1/2-inch overhang, then fold them under and crimp as desired. Par-bake for 10-12 minutes until lightly golden.
Step 2: If making a homemade crust, prepare your favorite recipe. Blind bake it by placing parchment paper or foil over the crust and filling with pie weights, dried beans, or rice. Bake for 15 minutes, then remove weights and parchment/foil and bake for another 5-7 minutes until lightly golden.
Step 3: In a large bowl, combine 6 cups of fresh pitted sweet cherries (or frozen, unthawed cherries). Add 1/2 cup granulated sugar, 1/4 cup cornstarch, 1 teaspoon almond extract, and 1/2 teaspoon ground cinnamon.
Step 4: Gently toss all the ingredients together until the cherries are evenly coated.
Step 5: In a separate medium bowl, combine 1 cup all-purpose flour, 1/2 cup rolled oats, 1/2 cup packed light brown sugar, and 1/4 teaspoon salt. Whisk these dry ingredients together.
Step 6: Add 1/2 cup (1 stick) unsalted butter, cut into small cubes and chilled. Using your fingertips or a pastry blender, cut the butter into the dry ingredients until the mixture resembles coarse crumbs with some pea-sized pieces of butter remaining.
Step 7: Pour the cherry filling evenly into the par-baked pie crust. Spread it out gently to ensure an even layer.
Step 8: Generously sprinkle the crumble topping over the cherry filling, covering it completely. Do not press it down too hard.
Step 9: Place the pie on a baking sheet to catch any overflow. Bake for 50-60 minutes, or until the crumble topping is golden brown and the cherry filling is bubbling thickly. If the topping browns too quickly, loosely tent the pie with aluminum foil during the last 15-20 minutes.
Step 10: Allow the pie to cool completely on a wire rack for at least 2-3 hours before slicing and serving. This cooling time is crucial for the filling to set properly.