Wash hands and prepare ingredients: Wash your hands thoroughly. Select fresh basil, oregano, yellow squash, zucchini, eggplant, and Roma tomatoes. Wash and thinly slice all vegetables uniformly.
Make the tomato sauce base: Heat olive oil in a saucepan over medium heat. Add minced garlic and finely chopped onion. Cook gently, stirring constantly to avoid burning, until softened and fragrant. Add canned crushed tomatoes and simmer the sauce until flavors meld and it thickens slightly.
Preheat the oven: Preheat the oven to approximately 300°F (150°C).
Assemble the ratatouille: Spread a smooth, even layer of the tomato sauce in the bottom of a baking dish. Arrange the sliced vegetables in an alternating pattern (eggplant, tomato, zucchini, yellow squash) in concentric circles or rows, layering them neatly to create an attractive pattern.
Bake the ratatouille: Lightly cover the assembled dish with parchment paper and bake in the preheated oven for approximately 45-60 minutes, until the vegetables are tender and cooked through.
Plate and garnish: Carefully remove the ratatouille from the oven. Plate by stacking small amounts of the cooked vegetables to build height and visual appeal. Drizzle lightly with olive oil and garnish with fresh parsley leaves around the plate edge. Finish by placing a single chive stalk on top as a final touch.