Preheat the oven to 375°F. Line an 8x8 inch baking dish with parchment paper and lightly spray with cooking spray.
In a large bowl, make the base/crumble by mixing the softened vegan butter, oat flour, ¾ cup of coconut sugar, and almond extract with a hand mixer until it resembles course sand.
Press ½ of the mixture into the bottom of the prepared baking dish and gently press down.
In a seperate bowl, add the rhubarb, strawberries, lemon juice, arrowroot starch, and remaining ¼ cup of coconut sugar. Stir to combine and evenly spread over the base in the prepared baking dish.
Evenly drop the remaining crumble mixture on top of the rhubarb, strawberry mixture. Sprinkle with choppd almonds.
Bake for 50-55 minutes until golden brown and bubbling. Allow to cool on a wire rack. Once cool, remove from the pan and cut into bars.