Preheat your oven to 375°F (190°C).
In a skillet over medium-high heat, brown the ground beef until fully cooked, then season with sea salt, black pepper, garlic powder, and dried oregano.
Add the fresh spinach to the skillet and stir until wilted, then remove from heat.
Cook the whole wheat lasagna noodle in boiling water until al dente, then drain and cut into three equal pieces.
Using a mandoline or sharp knife, slice the zucchini into very thin rounds to serve as low-carb layering bulk.
In a small individual-sized baking dish, spread a thin layer of marinara sauce on the bottom.
Begin layering by placing one piece of pasta, followed by a portion of the beef and spinach mixture, several zucchini slices, and a tablespoon of ricotta cheese.
Repeat the layers until all ingredients are used, finishing with the remaining marinara sauce and a sprinkle of mozzarella cheese.
Bake for 20-25 minutes until the cheese is melted and golden brown.