Preheat the oven to 350°F. Spray a 9x9-inch or 8x11-inch baking pan with cooking spray.
For the berry filling: Add the berries, sugar, flour, salt, lemon juice and vanilla to the prepared baking pan. Mix very well to evenly combine (you want everything to be completely mixed and coated here!) Bake for 10 minutes while you prep the topping.
For the crisp topping: In a medium bowl, combine the gluten-free oats, almond flour, brown sugar, cinnamon and salt.
Add the cold cubed butter and toss it in the mixture until each piece is coated.
Squish each cube of butter between your fingers to form small, thin sheets of butter. This will take some time, so keep working until the butter is no longer visible and the crisp mixture will hold together when squeezed in your hand.
Remove the berries from the oven. Sprinkle the topping evenly over the berries.
Bake for 35-40 minutes, until the topping is golden brown and berries are bubbling around the edges.
Remove from the oven and let cool for 10 minutes before serving.