Preheat your oven to 375°F (190°C). In a large mixing bowl, combine the blueberries, sugar, lemon juice, and flour. Stir gently until the berries are coated and the mixture begins to ooze and bubble slightly.
Pour the blueberry mixture into a baking dish, spreading it out evenly. Set aside while you prepare the crumble topping.
In a separate bowl, combine the oats, brown sugar, cinnamon, and salt. Add the cold butter pieces and use a pastry cutter or fork to cut the butter into the dry ingredients until the mixture resembles coarse crumbs.
Sprinkle the crumble topping evenly over the berry filling, covering all the fruit and allowing some to spill over the sides.
Bake in the preheated oven for 35-40 minutes, until the topping is golden brown and the filling is bubbling around the edges. The aroma of baked berries and toasted oats will fill your kitchen.
Remove from the oven and let cool slightly before serving. The cobbler should be bubbling and the topping crisp, offering a satisfying crunch with each bite.