First, pour a portion of the tomato sauce into the casserole dish, then place the zucchini slices on top. Now add the lasagna sheets and make sure that you press them well into the sauce so that the slices are well done. Spread some of the béchamel sauce on the lasagna sheets and layer the lasagna this way. Finish the lasagne with the rest of the tomato sauce, some béchamel sauce and I have added some vegan cheese on top!