Combine the flour, Creole seasoning and salt in a wide, flat-bottomed bowl (a soup bowl is perfect).
Rinse the trout fillets and pat dry. Dredge the fish through the seasoned flour, and knock off the excess. Place the fish in a pan on waxed paper and set aside.
Melt the butter in a saucepan over medium heat. When it begins to bubble, stir in 1/3 cup of the leftover seasoned flour and make a roux, stirring constantly, until it's a medium brown.
When the right color is reached, remove the roux from the heat and whisk in the stock, lemon juice, Worcestershire, and vinegar. Keep whisking until the sauce is smooth. Reduce the heat to the lowest setting to keep it warm while you prepare the fish.
You can pan-fry the fish in butter if you like, but it's more common in New Orleans to fry it in about an inch of 375-degree oil. Either way, cook till golden brown (about two minutes per side.)