Preheat oven to 375°F (190°C) and grease an 8x8 inch baking dish with butter or non-stick spray.
In a large mixing bowl, toss the blueberries with lemon juice, cornstarch, and granulated sugar until the berries are evenly coated.
Transfer the blueberry mixture into the prepared baking dish and spread into an even layer.
In a separate medium bowl, combine the gluten-free oats, almond flour, brown sugar, cinnamon, and sea salt.
Add the cubed cold butter to the oat mixture. Use a pastry cutter or your fingertips to work the butter into the dry ingredients until it forms pea-sized crumbs.
Sprinkle the crumble topping evenly over the blueberry base.
Bake for 35 to 40 minutes, or until the fruit filling is bubbling around the edges and the topping is golden brown.
Remove from the oven and allow the crisp to rest for at least 15 minutes to let the juices thicken before serving.