Preheat your oven to 400°F.
Butter a large baking pan. In a small saucepan, over medium-low heat, stir the butter, maple syrup, and apple juice together until the butter is melted. Increase the heat and bring it to a boil until it’s slightly reduced (about 5 minutes). Remove from heat, and stir in the cinnamon, all spice, and salt.
Arrange a layer of squash in the bottom of the baking dish. Arrange the rest of the apples and squash on top - some folks like to do it fancy (a layer of apples, another layer of squash, and then topped with alternating slices of apples and squash so it looks pretty like ratatouille), but we just mix them all together and dump them on top. Sprinkle with salt, and pour the maple syrup mix over top. Cover the dish with foil.
Bake 30-45 minutes, uncover it, and bake another 30-40 mins, occasionally basting it with the maple syrup mix.
Serve warm or at room temperature. So delicious!