Preheat your oven to 375°F (190°C).
Sprinkle the zucchini slices with salt and let them sit for about 10 minutes to draw out excess moisture. Pat them dry with paper towels.
In a medium bowl, combine the ricotta cheese, half of the mozzarella cheese, Parmesan cheese, garlic powder, Italian seasoning, and black pepper. Mix until well combined.
In a 9x13-inch baking dish, spread 1 cup of marinara sauce evenly on the bottom.
Layer half of the zucchini slices over the marinara sauce, followed by half of the ricotta mixture. Spread it evenly over the zucchini.
Repeat the layering with the remaining zucchini slices and ricotta mixture. Top with the remaining marinara sauce and sprinkle the rest of the mozzarella cheese on top.
Drizzle olive oil over the top and cover the dish with aluminum foil.
Bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 15 minutes, or until the cheese is bubbly and golden.
Let it cool for about 5 minutes before serving. Garnish with fresh basil leaves if desired.