Preheat your oven to 375°F (190°C).
Boil the lasagna noodles in salted water for 9 minutes or until al dente.
Drain and set aside.
In a skillet, heat olive oil over medium heat.
Sauté the onion, garlic, carrots, and celery until they are soft and fragrant.
Add spinach and cook for another 2 minutes until wilted.
In a mixing bowl, combine ricotta cheese, salt, and black pepper.
Stir well to blend the flavors.
In a baking dish, spread a layer of white sauce on the bottom.
Place a layer of cooked noodles over the sauce.
Add half of the sautéed vegetable mixture.
Spread a portion of the ricotta mixture on top.
Sprinkle a layer of mozzarella and Parmesan cheese.
Repeat the layers until all ingredients are used, finishing with cheese on top.
Cover the dish with aluminum foil.
Bake for 40 minutes, then uncover and bake for an additional 10 minutes until golden brown.