Preheat your oven to 375°F (190°C).
Cook the jumbo pasta shells in boiling salted water for 2 minutes less than the package directions until al dente, then drain and set aside.
In a medium skillet over medium-high heat, brown the ground turkey until fully cooked, breaking it into small crumbles.
Finely chop the fresh spinach and place it in a large mixing bowl.
Add the cooked turkey, ricotta cheese, egg, parmesan, sea salt, black pepper, garlic powder, and dried oregano to the spinach; mix until well combined.
Spread half of the marinara sauce onto the bottom of a small baking dish.
Stuff each cooked shell generously with the turkey and cheese mixture and arrange them in the baking dish.
Top with the remaining marinara sauce.
Cover with foil and bake for 20 minutes, then remove the foil and bake for another 5-10 minutes until the sauce is bubbling and the edges are slightly golden.