Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish.
Boil the whole wheat lasagna noodles in salted water according to package directions until al dente, then drain and set aside.
In a medium skillet over medium-high heat, brown the ground beef with the minced garlic, sea salt, black pepper, and dried oregano until fully cooked.
In a small bowl, combine the ricotta cheese, beaten egg, and chopped fresh spinach, mixing until well incorporated.
Spread a spoonful of marinara sauce on the bottom of the baking dish, then place one noodle (cut to fit if necessary) on top.
Layer half of the cooked beef, half of the ricotta mixture, and more marinara sauce over the noodle.
Repeat the layers with the remaining noodle, beef, ricotta, and sauce, finishing with a sprinkle of shredded mozzarella cheese.
Bake for 20-25 minutes until the cheese is melted and the edges are bubbling.