Preheat your oven to 350°F (175°C).
In a large bowl, combine the blueberries, lemon juice, granulated sugar, flour, and lemon zest. Mix well until the blueberries are evenly coated.
Transfer the blueberry mixture to a large baking dish, spreading it out evenly.
In a medium bowl, combine the oats, flour, light brown sugar, nuts, and salt. Add the melted butter or coconut oil and mix until the topping ingredients are well combined and crumbly.
Sprinkle the crumble mixture evenly over the blueberry filling.
Bake in the preheated oven for 35-40 minutes, or until the topping is golden brown and the blueberry filling is bubbly.
Let the crisp cool at room temperature for 30 minutes before serving to allow the filling to set properly.
Enjoy it warm with a scoop of vanilla ice cream or topped with homemade whipped cream.