Over medium heat, sauté the onion, pepper, jalapeño, celery, okra, salt, pepper, chili powder and garlic in olive oil for 5 to 7 minutes. The vegetables should wilt but not brown.
Add the flour and cook for 2 to 3 minutes, stirring constantly.
Add the tomato paste, diced tomatoes and stock. Cover and bring to a boil, then reduce the heat to medium-low and simmer for 25 minutes.
Add the rice and simmer for another 15 minutes.
Add the cooked chicken, and simmer until the chicken is heated through and the rice is tender.