Preheat the oven to 350℉ and have an 8x8 or 9x9-inch baking pan ready.
In a medium bowl, whisk together the 1 cup almond flour, 2 cups old fashioned rolled oats, and ½ cup light or dark brown sugar. Drizzle in the melted ½ cup unsalted butter and stir the mixture to moisten the dry ingredients. Place the topping in the fridge while you make the filling.
Make the Filling and Assemble
In a large bowl, toss together the sliced 4-5 apples, ¼ cup light or dark brown sugar, 1 teaspoon ground cinnamon, ¼ teaspoon ground ginger, and ¼ teaspoon fine sea salt
Spread the fruit out in an even layer in the baking pan. Take the topping from the fridge and sprinkle it evenly over the top of the fruit.
Place the crumble in the oven and bake for about 45 minutes, until the filling is bubbling and the topping is lightly browned and crisp.
Remove from the oven and place on a wire rack to cool for about 20 minutes before serving. The crisp is perfect served warm, at room temperature, or straight from the fridge.
Notes
CN's Crisp Tips
Chill the topping. Place the topping in the fridge to chill while I make the filling. This lets the butter firm up slightly, making for a crisper topping later. If you find that the topping is too firm when you take it out of the fridge, break it up with your hands before scattering it over the filling.
Let it rest. After removing the crisp from the oven, let it sit for at least 30 minutes so that the filling sets up a bit. I like to let my crisps rest even longer so that the filling can really gel (up to 1 or more hours).
Enjoy at any temperature. Crisp tastes amazing warm (after it's set!), at room temperature, or even straight out of the fridge.
Adjust the sweetness. You can add more or less of the amount of sugar specified in the recipe card, depending on your preference and how sweet the apples are.
Try another sweetener. I love maple syrup in the filling (and the topping, too, come to think of it) as its dark sweetness plays off of the juicy natural sweetness of the apples. You could also use honey. For a naturally sweet option, try coconut sugar in the topping and filling, or coconut sugar in the topping and maple syrup in the filling.
Dairy-free: As noted, non-dairy butter works great here. I also like melted coconut oil or a neutral oil such as avocado oil.
To serve: Vanilla ice cream is my favorite finish to crisp, and whipped cream or a drizzle of salted caramel sauce is also lovely. Or enjoy crisp at breakfast with regular or Greek yogurt.