Preheat the Oven. Preheat your oven to 375°F. Grease a 9-inch baking dish with butter or nonstick spray.
Prepare the Strawberry Filling. In a large bowl, combine sliced strawberries, sugar, cornstarch, lemon juice, and vanilla extract. Stir until the strawberries are well coated. Pour the strawberry mixture into the prepared baking dish, spreading it out evenly.
Make the Crumble Topping. In a separate bowl, mix together flour, oats, brown sugar, cinnamon, and salt. Pour in the melted butter and stir until the mixture forms a crumbly, sand-like texture.
Assemble and Bake. Sprinkle the crumble topping evenly over the strawberry filling. Bake for 35-40 minutes, or until the fruit is bubbling and the topping is golden brown and crisp.
Cool and Serve. Let the crumble cool for about 10 minutes before serving to allow the filling to set. Serve warm with vanilla ice cream, whipped cream, or fresh mint for an extra-special touch!