1 tablespoon arrowroot starch mixed with 1 tablespoon water
Preheat the oven to 350 degrees and line a 9x9 inch pan with parchment paper.
Spread the almonds out on a sheet tray. Bake for 7 minutes or until fragrant and golden. Set aside.
In a bowl, whisk together the oat flour, quick oats and salt. Add in the maple syrup and coconut oil. Use your hands to pinch the mixture together and thoroughly incorporate the coconut oil. The mixture should hold together when pinched and there should be no stray flour in the bottom of the bowl. Add in the walnuts, and knead to combine. Press 2/3 of this mixture into your prepared pan, pressing down to get rid of any cracks and form one solid piece. Bake for 15 minutes. Remove from the oven and cool for 5 minutes.
While the bottom crust is baking, add the frozen cherries into a saucepan. Heat over medium heat until the cherries are defrosted and the sauce is simmering. Use a potato masher to gently break the cherries into smaller pieces. Remove from the heat and add in the arrowroot starch mixture. Return to the heat and bring back to a simmer. Remove from the heat and set aside.
Pour the cherry mixture over the baked crust and sprinkle on the remaining crumble. Bake, uncovered, for 14 to 18 minutes more, until the topping is lightly firm to the touch. Let cool in the pan on a cooling rack for 45 to 60 minutes. Lift out the slab and slice it into squares or bars. Leftovers can be stored in an airtight container in the fridge for several days, or wrapped up and stored in the freezer.