First, chop the cooked turkey into 1-inch pieces, or shred by hand, and reserve. Next, in a 3 to 4 gallon stockpot over medium heat, add the butter and melt. Next, add the flour into the butter and cook together, stirring until a dark roux has been achieved (think popcorn smell).
Add the bacon renderings, celery, onions and bell peppers to the roux, cooking until the vegetables are softened. Next, pour a cup of the stock into the roux, mixing well to temper the roux. Then add the remaining stock and continue to cook for 30 minutes. Add the reserved turkey, the ham, file powder, garlic, salt and pepper, crushed chili peppers, thyme and bay, and cook another 30 minutes. Finally, add the okra and reduce the heat to low, cooking for 10 to 20 more minutes.
Prepare this one day or more in advance, as the gumbo does age well.