How to Make It
Preheat oven to 425°.
Combine first 6 ingredients in a large roasting pan. Bake at 425° for 1 hour or until wings are browned. Transfer contents of pan to a large Dutch oven. Add stock, parsley, thyme, and bay leaves to pan; bring to a boil. Cover, reduce heat, and simmer 2 1/2 hours. Strain mixture over a large bowl; discard solids. Cover bowl, and refrigerate at least 8 hours. Remove and discard fat layer on top of stock. Measure and reserve 8 cups of stock; save any remaining stock for another use.
Combine flour, 2/3 cup reserved stock, and 1/3 cup water in a bowl, stirring with a whisk until smooth. Bring remaining 7 1/3 cups stock to a boil in Dutch oven. Gradually add flour mixture, salt, and pepper, stirring with a whisk. Bring to a boil, and simmer 5 minutes.