To make the sauce: Put the skillet on the stove and turn the heat to medium-low. When the skillet is hot, add the oil. Add the onion and garlic and cook, stirring frequently, until tender, about 10-15 minutes.
Add the zucchini and basil or oregano and cook, covered, until the zucchini is just golden and tender, about 10-15 minutes, stirring every 5 minutes.
Add the tomatoes and water and stir well. Turn the heat down to low and cook, covered, for 10 minutes. Remove the lid and cook an additional 10 minutes.
Turn the heat off. Add the spinach and stir until the spinach is wilted.
Carefully slip 4 noodle pieces into the skillet, using their edges to slide them under to the bottom of the sauce, and using the spatula, push them down below the surface. Layer on another 4 noodle pieces, and then another 4, and push them all below the surface. Add the last 4 noodle pieces and spoon a little bit of the tomato mixture on top.
Add the ricotta, 1 tablespoon at a time, dotting the top with dollops. Sprinkle on the mozzarella and then the Parmesan cheese.
Reheat the skillet over low heat, cover and continue cooking until the cheese melts and the noodles are tender when you poke them with the tip of a knife, about 20 minutes. Sprinkle with the basil leaves. Turn off the heat and let the lasagna sit for 10 minutes.
Serve right away or cover and refrigerate up to 2 days.