Preheat the oven to 375ºF.
If using store-bought ricotta, transfer to a bowl. Add the Italian seasoning and stir to combine. If using tofu ricotta (recipe below), skip this step as the tofu ricotta already has the seasoning. Set aside in fridge.
Using a mandolin slicer, thinly slice the zucchini into long strips. You can also do this with a knife, but it's more difficult and tricky to get an even thickness.
Line a baking sheet with paper towels then lay the zucchini on top of the paper towel. Do this with two sheets (or until you've laid out all the zucchini strips). Sprinkle with sea salt and allow to sit for at least 15 minutes.
After 15 minutes, the zucchini should have released a lot of moisture. Pat them dry.
Now it's time to assemble the lasagna. In a baking dish (9x13 works well), add 1/2 cup sauce. Spread evenly with a spoon.
Add a layer of zucchini, completely covering the base of the pan. Next, add some ricotta (about 1/3- 1/2 cup) and smooth it over the zucchini with a spoon or your hands (hands are easier!). Next, add a thin layer of sauce (about 1/4 cup).
Repeat with the same layer pattern until you've used all your ingredients or you've filled the pan.
For your final layer, do a layer of zucchini, then top with 1/3 cup - 1/2 cup sauce. Spread evenly across the top. If using, sprinkle with vegan cheese.
Bake on the center rack for 40 - 45 minutes until the zucchini is cooked through.
Allow to cool for 10 - 15 minutes, then slice into 6 portions and serve.