Heat the oil in a large pot or Dutch oven over medium heat.
Working one vegetable at a time, add to the pot and saute for a minute, stirring. Then add the next vegetable, continuing until you've added everything up to the water.
Stir in the water, tomato paste, bay leaves, basil, salt, black pepper and red pepper flakes (you can leave them out if you want).
Cover. Reduce the heat to a slow simmer and cook 2 1/2 - 3 hours, stirring occasionally.