Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking dish.

Combine 2 cups of all-purpose flour, 1 cup of old-fashioned oats, ¾ cup of brown sugar, ½ cup of granulated sugar, ½ teaspoon of baking soda, and ¼ teaspoon of salt in a mixing bowl. Add 1 cup of melted unsalted butter and 1 teaspoon of vanilla extract, then mix until crumbly.

Press two-thirds of the crumble mixture into the bottom of the greased baking dish and bake for 10-12 minutes until golden.

Prepare the filling by tossing 4 diced apples with 1 tablespoon of lemon juice, 1 tablespoon of cinnamon, and ¼ teaspoon of nutmeg.

Layer the apple mixture over the baked crust and drizzle with ½ cup of salted caramel sauce.

Sprinkle the remaining crumble mixture over the apple and caramel.

Bake for an additional 30-35 minutes until golden brown.

Cool in the pan for 15-20 minutes, then sprinkle with sea salt before cutting into squares.