Step 1: Preheat your oven to 375°F (190°C). Line a 9x13 inch baking pan with parchment paper, leaving an overhang on the sides. Lightly grease the parchment.
Step 2: In a large bowl, whisk together the all-purpose flour, almond flour, 1/2 cup granulated sugar, light brown sugar, and salt.
Step 3: Add the cold, cubed unsalted butter to the dry ingredients. Use a pastry blender or your fingertips to cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces.
Step 4: Reserve about 1.5 cups (approx. 200g) of this mixture for the crumble topping. Press the remaining mixture evenly into the bottom of the prepared baking pan. Bake for 12-15 minutes, or until lightly golden.
Step 5: While the crust is baking, prepare the apricot filling. In a medium bowl, combine the chopped fresh apricots, 1/4 cup granulated sugar, lemon juice, and cornstarch. Stir gently to coat.
Step 6: Once the crust is lightly golden, remove it from the oven. Carefully spread the apricot mixture evenly over the warm crust.
Step 7: Sprinkle the reserved crumble mixture evenly over the apricot filling.
Step 8: Return the pan to the oven and bake for another 35-40 minutes, or until the crumble topping is golden brown and the apricot filling is bubbly.
Step 9: Remove from the oven and place on a wire rack to cool completely for at least 2-3 hours. This is crucial for the bars to set properly.
Step 10: Once completely cooled, use the parchment paper overhang to lift the slab of bars from the pan. Place on a cutting board and cut into 16 squares. Serve and enjoy!