Preheat the oven to 180°C fan (356°F fan).
Mix the frozen berries with flour, sugar, lime zest and juice, vanilla paste, and maple syrup in a medium-sized bowl.
Use a spoon to ensure the berries are covered in the flour mixture.
Place the berries in a medium baking dish or cast iron skillet.
To make the topping add the oats, brown sugar, flour, butter, and sea salt to a medium bowl.
Using your hands or a mixer on low, crumble the butter into the remaining ingredients until it resembles large streusel pieces or clumps.
Arrange the crumble mixture on top of the berries in an even layer.
Bake for about 40-45 minutes until the base is bubbly and the topping is golden brown.
Serve warm with ice cream, whipped cream, or sour cream.