Preheat your oven to 375°F (190°C) and prepare the red potatoes by placing them in a pot of boiling water for 3-4 minutes.

In a medium saucepan, melt 2 tablespoons of butter over medium heat, whisk in 2 tablespoons of flour to make a roux then add 2 cups of warm milk gradually, whisking until thickened.

Spray a 9x13 inch baking dish and layer the bottom with tomato basil sauce, then sprinkle with minced garlic and thyme, and drizzle with olive oil.

Drizzle the prepared Béchamel sauce over the tomato sauce layer and swirl it slightly with a spatula.

Layer the thinly sliced eggplant, zucchini, yellow squash, and bell pepper in a spiral pattern over the Béchamel, drizzling olive oil and seasoning between layers.

Cover the dish with parchment paper and bake for 55-60 minutes until vegetables are tender and bubbling.

Let the casserole cool for about 5 minutes before serving, ideally accompanied by crusty bread.