Preheat oven to 400F (200C). Lay zucchini planks on paper towels, sprinkle with salt, and let sit for 15 minutes to draw out moisture.
Pat zucchini dry and roast on a baking sheet for 10-12 minutes to further reduce water content; set aside and lower oven to 375F (190C).
In a large skillet, heat olive oil over medium heat. Sauté onion and garlic until translucent, then add ground turkey and cook until browned.
Stir marinara sauce into the turkey mixture and simmer for 10 minutes; season with oregano, salt, and pepper.
In a medium bowl, combine ricotta cheese, egg, chopped parsley, and 1/4 cup of parmesan cheese.
Layer 1: Spread 1/2 cup of turkey meat sauce on the bottom of a 9x13 inch baking dish.
Layer 2: Arrange a single layer of roasted zucchini planks over the sauce.
Layer 3: Spread half of the ricotta mixture over the zucchini.
Layer 4: Add half of the remaining turkey meat sauce.
Layer 5: Arrange another layer of zucchini planks.
Layer 6: Spread the remaining ricotta mixture and turkey meat sauce evenly.
Layer 7: Top with mozzarella cheese and the remaining 1/4 cup of parmesan cheese.
Bake for 35-40 minutes until the cheese is golden and bubbling. Let stand for 15 minutes before slicing to allow layers to set.