Heat the oil in a large pot over medium heat. Add the onions, carrots, celery, bell pepper and garlic and cook until firm/tender, about 3-4 minutes. Stir in flour and curry powder and mix until well combined. Slowly pour in vegetable stock, mixing steadily. Add remaining ingredients, except peas, and bring to a simmer. Gentle simmer until all vegetables are cooked through, about 20 minutes. Mix in the peas and adjust seasoning. Serve, if desired, over steamed rice.