Method

1. Preheat an oven to 350 degrees.
2. Add the almond flour, oats, sugar, and butter in a mixing bowl. Use your hands to work the butter into the flour, sugar, and oats until it is well combined and forms a dough like consistency.
3. Press 2/3 of the crumb-crust mixture into a 8×8 pan lined with parchment paper. Bake the crust for 15 minutes, remove from the oven, and set aside.
4. In a medium saucepan, combine the blueberries, maple syrup, cinnamon, and vanilla extract over medium-high heat. Use a wooden spoon or potato masher to mash the blueberries and break them down. Bring the blueberry mixture to a boil and then lower the heat and let simmer for 10 minutes while constantly stirring.
5. When the blueberries have all burst and turned a dark purple color, whisk the lemon juice and arrowroot starch in a small bowl to make a slurry. Turn off the heat, and pour the slurry mixture into the blueberries. Stir until the blueberries have thickened into a jam like consistency.
6. Pour the blueberry jam on top of the crust and use a spatula to spread it evenly over the crust. Sprinkle the remaining crumb topping evenly over the jam.
7. Let the bars bake at 350 degrees for 25-30 minutes until the jam is bubbly around the edges and the top is golden brown.
8. Let the bars come to a complete cool. Slice into squares and enjoy!