**Prepare the zucchini**
Lay the zucchini slices on a clean kitchen towel and sprinkle with salt. Let them sit for 15–20 minutes to draw out excess moisture. Pat dry with another towel to prevent a watery lasagna.
**Make the meat sauce**
Heat olive oil in a large skillet over medium heat. Add the ground turkey and cook until browned, about 5–7 minutes. Stir in the diced onion and minced garlic, cooking until fragrant and softened. Add the marinara sauce, basil, oregano, red pepper flakes (if using), and salt and pepper to taste. Simmer for 10 minutes.
**Mix the cheese filling**
In a mixing bowl, combine ricotta, mozzarella, Parmesan, egg, and parsley. Mix until smooth and set aside.
**Assemble the lasagna**
Preheat your oven to 375°F (190°C). Spread a thin layer of meat sauce on the bottom of a 9x13-inch baking dish. Add a layer of zucchini slices, followed by a layer of the ricotta mixture, and then the meat sauce. Repeat the layers, finishing with a layer of meat sauce and a sprinkle of mozzarella cheese on top.
**Bake**
Cover the dish with foil and bake for 30 minutes. Remove the foil and bake for an additional 15–20 minutes, or until the cheese is bubbly and golden brown.
**Rest and serve**
Let the lasagna rest for 10 minutes before slicing. Garnish with fresh parsley and serve warm.