1. Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish.
2. In a large bowl, combine the strawberries, peaches, granulated sugar, lemon juice, and cornstarch. Toss until the fruit is well-coated.
3. Pour the fruit mixture into the prepared baking dish, spreading it evenly.
4. In another bowl, mix together the flour, oats, brown sugar, cinnamon, and salt. Stir in the melted butter until the mixture becomes crumbly.
5. Sprinkle the crumble mixture over the fruit, covering it completely.
6. Bake in the preheated oven for 35-40 minutes, or until the topping is golden brown and the fruit is bubbling.
7. Let it cool for a few minutes before serving, allowing the juices to thicken slightly.

Remember, the best part about this recipe is that it doesn’t demand perfection. If a little fruit peeks through the topping or the edges get a bit crispy, it only adds character.