Place a clean kitchen towel (or several layers of paper towels) inside a rimmed baking sheet. Lay the eggplant and zucchini slices on the kitchen towel and sprinkle ¾ teaspoon salt over one side of the eggplant slices. Flip the eggplant and zucchini slices around and sprinkle another ¾ teaspoon of salt over the opposite side.
Let the salted eggplant and zucchini sit at room temperature for 30 to 40 minutes, until beads of moisture form on the surface.
Preheat the oven to 425°F and line 2 baking sheets with parchment paper or a silicone baking mat.
Use a clean kitchen towel or paper towels to pat the eggplant and zucchini slices dry and remove some of the salt. Place your eggplant and zucchini slices on the lined baking sheets.
Pour the olive oil into a small bowl, and add the grated garlic, dried oregano, red chili flakes, and black pepper to the oil. Use a pastry brush to brush both sides of the eggplant and zucchini slices with the herbed olive oil. If you don’t have a pastry brush, you can spoon the olive oil onto the eggplant and zucchini slices.
Cook the eggplant and zucchini in the oven until the centers are completely soft and the eggplant and zucchini are golden brown, about 20 to 25 minutes. Then remove and flip your veggies and coat again with the olive oil mixture, and place back in the oven for another 20 to 25 minutes. The zucchini might cook faster and need to be removed before the eggplant is done.
Toast your bread of choice and start to assemble your sandwiches! I like to melt the cheese on the bottom piece of bread, followed by eggplant, zucchini, tomatoes, I HIGHLY recommend seasoning your tomato slices with some salt and pepper before adding to the sandwich, spinach, and then I like to add my condiment to the top piece of bread and sandwich it all together and enjoy!
Store your leftovers separately in the fridge for up to 4 days.