Cook lasagna noodles according to the package instructions.
While the pasta is cooking, add the spinach in a small saute pan. Add a splash of water and allow spinach to wilt. Transfer the spinach to a colander and press out as much additional as possible. Set aside.
Once the noodles have finished cooking, line the bottom of a 9" x 13" with a thin layer of tomato sauce. Add a layer of noodles and some dollops of the ricotta. Spread evenly across the noodles. Sprinkle with Italian seasoning (if using), then top with some spinach and about 1/4 cup of tomato sauce and again spread evenly across the layer.
Repeat this step for another two or three layers (depending on the size of your pan and noodles).
Top with a final layer of noodles, spread with sauce and sprinkle with the shredded vegan cheese.
Bake in the center of the oven for about 35 - 45 minutes, until the cheese has melted and the lasagna is fully cooked and heated through.
Cool for about 10 minutes, then slice and serve immediately. Garnish with red pepper flakes and some fresh herbs if desired!