Preheat oven to 350 degrees F. Line an 8 x 8 inch baking pan with aluminum foil and then grease it. I use an olive oil spray to grease it. Leave a flap of aluminum foil on either side of the pan.
In a medium bowl, add 2 cups of mixed berries, 2 Tbs lemon juice, ¼ cup coconut sugar and 2 tsp tapioca flour. Mix together and set aside.
In another medium bowl, add 1 cup almond flour, ¼ cup tapioca flour, 1 cup rolled oats, ½ cup coconut sugar, ½ tsp cinnamon, and ¼ tsp salt. Mix with a fork until blended.
In a third separate bowl, mix the melted coconut oil and egg yolk. Then, add the coconut oil mixture to the rolled oat mixture until everything is wet.
Remove 1 cup of the oat mixture and set it aside to use as the crumble on top. Press the remaining oat mixture left in the bowl into the bottom of the pan. Use a fork to press the mixture into the pan.
Evenly distribute the berries on top of the pressed down mixture in the pan.
Grab the mixture that was set aside and sprinkle on top of the berries.
Bake for 45-50 minutes or until you see the berries bubbling and the top of the crumble turning golden brown.
Let everything cool for one hour, then remove the bars from the pan by lifting the aluminum foil flaps. Let the bars cool for another 30 minutes or so. It is easier to cut into the bars when they are cool.
Notes
Note: if using frozen berries, Use 1 tablespoon of lemon juice instead of two and bake for 55 mins.