01 - Preheat oven to 350°F (175°C). Line a 9-by-13-inch baking pan with parchment paper, leaving an overhang for easy removal.
02 - In a large bowl, combine flour, oats, brown sugar, cinnamon, and salt. Add chilled butter and cut in using a pastry blender or fingertips until mixture resembles coarse crumbs.
03 - Press half of the crumb mixture firmly into the base of the prepared pan to form an even layer.
04 - Toss diced apples with granulated sugar, flour, and cinnamon in a medium bowl until apples are well coated.
05 - Spread apple filling evenly over the crust. Drizzle caramel sauce over the apple layer. Sprinkle remaining crumb mixture evenly on top.
06 - Bake for 35–40 minutes, until topping is golden brown and apples are tender. Remove from oven and cool completely before cutting into bars.