Preheat oven to 350ºF and add the blueberries to a 2-quart baking dish. Sprinkle them with cinnamon and arrowroot starch, and stir well.
To make the topping, add the almond flour to a large bowl, along with the salt, coconut, and walnuts. Stir well, then add in the melted coconut oil and maple syrup. (If using honey, you may want to melt the coconut oil in a saucepan over low heat first, then add in the honey to make sure it's melted, before you stir everything together.)
Sprinkle the topping over the blueberries, and lightly press the mixture with your hands to flatten it out. You don't want any pieces sticking up higher than the rest, or they could burn before the rest of the crumble topping is golden. Bake for 30 to 35 minutes, until lightly golden on top.
Let the blueberry crisp cool for 15 to 20 minutes before serving. It may look soupy at first, but it will firm up as it cools, with the topping becoming very crispy. Serve warm, with ice cream or coconut whipped cream on top.
Nutrition information is for 1 of 10 servings. This is just an estimate, and not a guarantee. For a lower-calorie dessert, you can make the portion smaller. A little bit goes a long way, since it's so nutrient dense!