Preheat oven to 350 F and line a baking tray with parchment paper.
Filling: a) In saucepan, bring berries, sugar and orange juice to a boil. Reduce heat and simmer until tender, about ten minutes. Whisk in 4 teaspoons of whole wheat flour until thickened.
Filling: b) Refrigerate until cooled.
Base and Topping: a) In large bowl, stir together the oats, the rest of the flour, brown sugar, sea salt and baking soda.
Base and Topping: b) Cut in the butter to form a crumbling mixture.
Base and Topping: c) Reserve 1 ½ cups of the crumbs and pat evenly onto your lined baking tray.
Base and Topping: d) Spread the berry mixture over the base. Crumble the reserved mixture topping over the berry mixture.
Base and Topping: e) Bake in the oven until golden brown and firm to the touch, about 40-45 minutes.
Base and Topping: f) Remove from the oven and allow to cool.