Heat a Dutch oven or large pot over medium heat. Add the vegetable oil and flour and cook, stirring constantly, until the roux mixture is dark brown, about 10 minutes. Add the onion, celery, peppers, garlic, salt, black pepper, Old Bay, and cayenne. Cook the vegetables until tender, stirring often, about 10 minutes.
Stir in the tomato paste and cook for 1 more minute. Add the vegetable stock, okra, bay leaves and thyme. Bring the mixture to a boil, reduce heat to medium-low and simmer, uncovered, for 20 minutes. Stir in the kale and simmer for another 5 minutes. Stir in the green onions and serve immediately in shallow bowls over steamed rice.