Preheat the oven to 350°F (175°C) and get out an 8"x8" (20cmx20cm) pan.
Mix the maple syrup, lemon juice, arrowroot powder, cinnamon, nutmeg, and salt together in a large bowl.
1/4 cup (60 ml) maple syrup, 1 tablespoon lemon juice, 1 tablespoon arrowroot starch, 1 teaspoon ground cinnamon, 1/4 teaspoon ground nutmeg, 1/8 teaspoon salt
Peel the apples, core and cut into 1/3" pieces. Place the apples in the maple syrup mixture and stir until the apples are well coated in the mixture. Place in the ungreased pan.
5 1/2 cups apples
In a medium mixing bowl, stir together the almond flour, coconut flour and cinnamon. Then add the coconut oil, maple syrup and salt and mix until combined.
3/4 cup (75 grams) finely ground blanched almond flour, 1 tablespoon (8 grams) coconut flour, 2 1/4 teaspoons ground cinnamon, 3 tablespoons (42 grams) refined coconut oil, 3 tablespoons maple syrup, less than 1/4 teaspoon salt
Pulse the pecans or walnuts in a food processor a few times until they're in small pieces (about 1/8" in size). You can also chop them by hand but the food processor takes a lot less time. Stir the nuts into the topping mixture.
1 cup pecans
Drop walnut-sized pieces of topping over the apples. Gently press down any nuts that are sticking out so that they don't burn.
Bake for 40-50 minutes or until the topping is brown and crisp and the apples are bubbling. The topping will crisp up much slower than a traditional crisp, but don't worry as it will crisp up towards the very end of the baking time. Cover the crisp with foil if the topping starts to brown too early.
Let cool for 10 minutes and serve. If not serving immediately, once cool, loosely cover with a piece of plastic wrap (so the topping doesn't go soft). If storing overnight, properly cover the crisp with plastic wrap. Do note that the topping gets soft on the second day.