Make the crumble mixture

• Combine the flour, rolled oats, brown sugar, cinnamon and salt in a bowl.
• Pour in the melted butter and mix until crumbly and evenly moistened.

Build the base

• Press about two thirds of the crumble mixture firmly into a greased baking dish to form an even base.
• Set the remaining crumble aside for the topping.

Prepare the apple filling

• Toss the sliced apples with the lemon juice, cornstarch and a little cinnamon.
• Spread the apples evenly over the base.

Add topping and bake

• Scatter the reserved crumble over the apples.
• Bake at 180 °C until golden and the apples are tender.

Finish with caramel

• Let the bars cool completely in the dish, then cut into squares.
• Drizzle with the salted caramel sauce and sprinkle with flaky sea salt.