In a large Dutch oven or heavy soup pot, heat the oil over medium high heat until hot, almost smoking. Gradually whisk in the flour, being careful not to splash the mixture so you don't get burned. Reduce the heat to low and cook and stir the roux continuously until medium brown and smoth, about 20 to 30 minutes.
Increase heat to medium high. Add the onion, green onions, bell pepper, celery and stir until the vegetables are wilted but not browned, about 7 minutes. Add the garlic, chile pepper, thyme, salt, black pepper, and cayenne. Reduce the heat to low and cook to allow the flavors to marry, about 20 minutes.
Whisk in the warm stock in batches to prevent splattering. Add the bay leaf, then bring back to a boil over high heat. Reduce the heat to medium-low and simmer for 30 minutes. Taste and add salt as desired. Add the okra, shrimp, oysters, and crab and simmer until just cooked, another few minutes. Taste and adjust seasonings with salt and pepper. Remove from the heat and let stand for 1 hour for the flavors to mingle. Remove and discard the bay leaf.
Return the pot to medium low heat just until the soup is hot again. Spoon into serving bowls, add hot rice as desired, and sprinkle with parsley.