Step 1

Preheat the oven to 375°F (190°C). Line a 9 x 9-inch (23 cm by 23 cm) pan with foil. Spray the foil with baking spray and line the foil with parchment, cut to fit the size of the pan with a 1-inch (2.5 cm) overhang on all sides. The layer of foil will allow you to lift the bars out of the pan cleanly and the parchment will keep the bars from sticking to the foil.

Step 2

Put rolled oats, brown rice flour, tapioca starch, brown sugar, salt, baking soda, wal­nuts, and cinnamon in a large bowl. Toss with your hands or a wooden spoon to combine. Add coconut oil and mix, using your hands or a wooden spoon, until the crumble mixture holds together in large clumps.

Step 3

Spread two thirds of the crumble mixture in the bottom of the pan and press down firmly to create an even layer, making sure the mixture reaches into the corners as well. Spread the fruit preserves over the crust, leaving ½ inch (12 mm) of space around the edges. Scatter the berries over the jam. Sprinkle with the remaining crumble, leaving space so that the berries show through.

Step 4

Bake for 40–45 minutes, rotating between upper and lower oven racks halfway through baking, until the bars are golden brown, and the berries are bubbling. Allow to cool completely in the pan before transferring to the refrigerator to chill for at least 2 hours before cutting into 12 bars.