Preheat oven to 375°F. Slice squash halves into 1/2" half-moon-shaped slices. Spray a large baking sheet with a light dusting of oil and sprinkle with a little sea salt and pepper. Place the slices on the sheet in a single layer. Lightly spray the tops and sprinkle with salt and pepper. Bake until the slices are tender, about 35 minutes. Remove from oven and set aside to cool; lower oven temperature to 350°F.
Place ricotta, kale, garlic and 1/4 teaspoon salt into a bowl and combine. Set aside.
Assemble the stacks: Coat the bottom of a 9" x 13" baking dish with a light layer of sauce. Lay 12 Polenta rounds side by side and season with a little salt and pepper; cover with sauce. Next, top each round with squash slices facing each other, trim to fit neatly. Top each set of squash with the ricotta-kale mixture and smooth out. Top with more sauce, followed by a layer of polenta and the last layer of squash. Pour over the remainder of sauce and top each stack with Mozzarella cheese, followed by Parmesan cheese.
Cover with foil and bake for about 40 minutes. Uncover for the last 10 minutes or until cheese is golden and bubbly. Remove from oven and rest 15 minutes before serving.