Mix together the flour, brown sugar, and sugar.
Then slice cold butter into the dry ingredients, and mix together with a pastry blender. It will form into a nice crumbly mixture.
Top off your pie with the crumble topping, making sure you crumble it all up around the edge, as well.
Place your pie plate on a baking sheet, and bake at 375° F for about 1 hour, possibly a little longer depending on whether or not your crust is done.
Once the pie is done, take it out of the oven, and allow it to cool on a wire rack, 'til you're ready to slice it up and serve it.