✓ Peel, core, and slice 6 cups of firm apples such as Granny Smith or Honeycrisp.

✓ Place sliced apples in a large bowl, sprinkle with 1 tablespoon lemon juice to prevent browning, and toss gently until evenly coated.

✓ Preheat the oven to 350°F (175°C). Grease an 8-inch square baking dish.

✓ In a medium bowl, mix together 3/4 cup rolled oats, 1/2 cup all-purpose flour (or gluten-free flour blend for gluten-free version), 1/2 cup brown sugar, 1/2 teaspoon ground cinnamon, and 1/4 teaspoon salt. Stir in 6 tablespoons cold unsalted butter or vegan margarine/coconut oil cut into small pieces until the mixture resembles coarse crumbs.

✓ Spread the apple slices evenly in the prepared baking dish.

✓ Sprinkle the oat topping over the apples, pressing down gently to ensure it adheres well and covers them entirely.

✓ Bake for 25-30 minutes or until the topping is golden brown and the edges of the apples are soft but still hold their shape. Ensure the filling is bubbling slightly around the edges when done.