Preheat the oven to 300°.
Spray the bottom of a 9x13” glass baking dish with cooking spray.
Add half the onions, half the leeks and 4 small roma tomatoes, sliced.
Sprinkle with 1/4 teaspoon salt and 1/4 teaspoon oregano.
Add a layer of eggplant and sprinkle with 1/2 teaspoon salt.
Add another four roma tomatoes in slices, sprinkle with black pepper, basil, marjoram and thyme (at least ¼ tsp. each).
Add a layer of zucchini and yellow squash and sprinkle again with marjoram and thyme.
Add another layer of eggplant.
Sprinkle with about ¼ tsp. salt to cover well.
Sprinkle with marjoram and thyme.
Add the bell pepper rings.
Sprinkle with at least ¼ tsp. each of basil, oregano, marjoram and thyme.
Add remaining onions, leeks, then 4 tomatoes.
Place minced garlic overtop the tomatoes.
Sprinkle with ½ tsp. pepper, and at least 1/4 teaspoon each of oregano, basil, marjoram and thyme, and 1/4 teaspoon salt.
Press the vegetables down a bit with a spatula.
Drizzle the avocado or olive oil over top. Bake for 2 to 2 1/2 hours, uncovered.
To eliminate soggy veggies, press veggies down with the back of a spatula several times during baking.
Let cool for about 10 minutes before serving.