Preheat your oven to 375°F (190°C).
Cook the lasagna noodles according to package instructions in a large pot of boiling salted water. Drain and set aside.
In a frying pan, heat olive oil over medium heat. Add minced garlic and sauté for about 1 minute until fragrant.
Add fresh spinach to the pan and cook until wilted (or heat frozen spinach until warmed). Season with salt, pepper, oregano, and basil. Remove from heat.
In a mixing bowl, combine ricotta cheese, egg, and half of the Parmesan cheese. Mix until smooth and set aside.
In the bottom of the baking dish, spread a thin layer of marinara sauce.
Layer 3 lasagna noodles over the sauce. Then spread half of the ricotta mixture, followed by half of the spinach mixture, and a third of the mozzarella cheese.
Repeat the layers: marinara sauce, 3 lasagna noodles, remaining ricotta mixture, remaining spinach, and another third of mozzarella cheese.
Top the final layer with the remaining 3 noodles, the rest of the marinara sauce, the remaining mozzarella cheese, and the remaining Parmesan cheese.
Cover the baking dish with aluminum foil and bake for 30 minutes.
Remove the foil and bake for an additional 15 minutes, or until the cheese is bubbly and golden.
Allow to cool for 10 minutes before slicing and serving.