Preheat your oven to 375°F (190°C).
Cook the manicotti shells in boiling water for 2 minutes less than the package directions so they remain firm; drain and set aside.
In a skillet over medium heat, add the olive oil and minced garlic, followed by the ground turkey, cooking until the meat is browned and crumbled.
Add the fresh spinach to the skillet and stir until just wilted, then remove from heat and let the mixture cool slightly.
In a medium bowl, combine the cooked turkey and spinach mixture with the ricotta cheese, dried oregano, sea salt, and black pepper.
Carefully stuff each manicotti shell with the turkey and cheese mixture using a small spoon or piping bag.
Spread half of the marinara sauce in the bottom of a small baking dish, arrange the stuffed shells on top, and cover with the remaining sauce.
Sprinkle the mozzarella and parmesan cheese evenly over the top.
Cover the dish with foil and bake for 20 minutes, then remove the foil and bake for an additional 5-10 minutes until the cheese is melted and bubbly.