Preheat your oven to 350°F (175°C).
Prepare a baking dish by greasing it lightly with butter or cooking spray.
In a large bowl, toss the sliced apples with lemon juice, sugar, cinnamon, nutmeg, and salt until evenly coated.
Transfer the apple mixture into the prepared baking dish, spreading it out evenly.
In another bowl, combine oats, flour, brown sugar, and melted butter, stirring until crumbly.
Sprinkle the crumble mixture evenly over the apples, covering them fully.
Bake in the preheated oven for 30-35 minutes, until the apples are bubbly and the topping is golden brown.
Let the dish cool for a few minutes before serving to allow the juices to settle.
