Sprinkle the eggplant slices lightly with salt and place on paper towels for 30 minutes to drain. Mix bread crumbs and oregano on a plate. Dry the eggplant slices, dust with flour, dip in beaten eggs, and cover with bread crumb mixture. Heat the olive oil in a skillet over medium heat and saute the eggplant slices until medium brown, about 5 minutes per side. Place a thin coating of marinara sauce in the bottom of a baking pan large enough to hold the eggplant in a single layer. Arrange the eggplant slices on the sauce, sprinkle with the Parmesan, and place a slice of mozzarella or Swiss cheese on top of each eggplant slice. Cover with the remaining marinara sauce. Bake in a 325F (165C) oven for 20 to 25 minutes.