Preheat the oven to 350°F (175°C). Line an 8-inch square baking pan with parchment paper, leaving an overhang for lifting out the bars.

Slice the rhubarb into small pieces. Hull and chop the fresh strawberries.

Combine the chopped rhubarb, strawberries, orange juice, 1/4 cup coconut sugar, and cornstarch in a saucepan. Stir until the cornstarch is evenly dispersed.

Cook the fruit mixture over medium heat for 8-10 minutes. Stir until the fruit softens and the filling becomes thick and glossy.

Combine 1 1/2 cups rolled oats, almond flour, 1/4 cup coconut sugar, and sea salt in a mixing bowl. Stir until evenly mixed.

Pour 1/3 cup melted coconut oil into the oat mixture. Mix until it forms a moist, pressable dough.

Press the oat-almond dough firmly and evenly into the lined baking pan. Bake for 15 minutes, until lightly golden around the edges.

Combine the remaining 1/2 cup rolled oats, gluten-free all-purpose flour, remaining 1/4 cup coconut sugar, and remaining sea salt in a second mixing bowl. Stir to combine.

Add the remaining melted coconut oil to the oat mixture. Mix with a fork or spoon until large crumbly clusters form.

Spread the warm strawberry-rhubarb filling over the partially baked crust. Smooth it into an even layer.

Sprinkle the oat crumble evenly over the fruit filling. Gently press only the largest crumbs into place.

Bake for 30-35 minutes, until the crumble is golden brown and the fruit filling bubbles at the edges. Transfer the pan to a wire rack.

Cool the bars completely in the pan for at least 60 minutes. Lift out using the parchment paper and cut into 9 squares.