Preheat your oven to 375°F (190°C).
Cook the lasagna noodle in a pot of boiling salted water until al dente, then drain and set aside on a clean surface.
In a medium non-stick skillet over medium-high heat, brown the ground beef until fully cooked and no pink remains.
Add the minced garlic, sea salt, black pepper, and dried oregano to the beef, sautéing for 1 minute until the spices are fragrant.
Stir the fresh baby spinach into the beef mixture until it is just wilted, then remove the skillet from the heat.
In a small bowl, stir the ricotta cheese until it is creamy and smooth.
Spread 2 tablespoons of the marinara sauce onto the bottom of a small individual-sized baking dish.
Cut the cooked lasagna noodle into three equal pieces to fit your baking dish.
Place one piece of the noodle over the sauce, followed by half of the beef and spinach mixture, a dollop of ricotta, and a spoonful of marinara.
Repeat the layer with the second piece of noodle, the remaining beef mixture, the remaining ricotta, and more sauce.
Top with the final piece of noodle, the rest of the marinara sauce, and a sprinkle of shredded mozzarella cheese.
Bake for 15-20 minutes until the cheese is melted and the edges of the lasagna are bubbling.