Preheat the oven to 180°C.
Mix the blueberries, sugar, and lemon juice, and place them in an oven-safe dish.
In a bowl, combine the flour, sugar, and butter, and mix by hand until you get a crumbly texture.
Sprinkle the crumble mixture evenly over the blueberries.
Bake in the oven for 25–30 minutes until the top is golden brown, then remove.