Preheat the oven to 350 degrees.
Line a 9x9 inch baking pan with parchment & give a light spritz with cooking spray or oil.
Combine the flour, sugar, and salt in a medium bowl.
Cut the butter into 1/2-inch cubes, and add to the flour mixture.
Using a fork for pastry cutter, cut the butter into the dry mixture until it resembles coarse crumbs.
Remove ¾ cup of the mixture to use as the topping & set it aside.
Press the remaining mixture into the bottom of the prepared pan, and bake for 10-12 minutes.
Cool for 10-15 minutes while you mix the filling.