Pour drippings from the roasting pan into a saucepan and set aside. Place the roasting pan over medium heat; add ¼ cup of turkey stock to deglaze, using a spatula to scrape up the brown bits on the bottom. Add the contents of the roasting pan to the saucepan.
Pour off and set aside nearly all the drippings, leaving ¾ cup in the saucepan. Set the saucepan over medium heat and whisk in the flour to make a roux. Continue whisking until the flour is evenly incorporated; then add another ½ cup of the reserved drippings. Whisk continuously until the roux thickens to a brown paste.
Slowly add in the rest of the stock, a little at a time, whisking between additions until smooth. Once all the stock has been added, bring to a low boil to make a thick, rich gravy, 2 minutes. Add salt, vinegar, and pepper to taste, then stir to combine. Makes about 1½ cups of gravy.