Tip the cooked turkey so any juices in the cavity run into the roasting pan, then move the bird to a board to rest. Look at the bottom of the pan. If it looks dry in spots, pour in 1 cup of low-sodium broth and simmer it over medium-high heat, then turn off the heat.
Scrape up all the browned bits with a wooden spoon, since they hold huge flavor. Pour everything through a fine-mesh strainer into a heatproof bowl or measuring cup. Throw away the solids that stay in the strainer.
Let the drippings sit for about 10 minutes so the fat floats to the top. You can chill them for a few minutes if you are in a hurry. Skim off the fat with a ladle and measure out 1/4 cup, topping it up with oil or melted butter if you are short.
Now measure the drippings that are left in the bowl. You want a total of 2 cups of liquid for this recipe. If you are short, simply add low-sodium broth until you reach that amount.
Heat the 1/4 cup of fat in a medium saucepan over medium-high heat until it is hot. Whisk in the flour and cook for 1.5 to 2 minutes, until it bubbles and turns slightly darker. If you like, pour in a splash of sherry or wine now and let it sizzle for a moment.
Slowly whisk in the drippings, adding the minced herbs if you are using them. Keep whisking until the gravy comes to a boil. Lower the heat and simmer for a few minutes if you want it thicker, then season with salt and pepper to taste.