Take the pan the turkey was roasted in and pour all the drippings into a glass measuring cup that can accommodate 1 quart of liquid. Leave any browned bits on the bottom of the roasting pan. (These are actually quite tasty and help give the gravy its flavor.)
Let the drippings stand until the fat rises to the top of the measuring cup. Spoon off the fat and reserve.
Add stock so that there are 4 cups of liquid in the measuring cup.
Set the roasting pan over medium-low heat. (You may need to use two burners at once.)
Spoon out 6 tbsp. of the reserved fat and put it back in the roasting pan. Sprinkle the flour over the fat and whisk.
Whisk flour and fat for 1 to 2 minutes until the flour turns a nice golden-brown color.
Pour the drippings and stock mixture into the roasting pan and scrape off the encrusted bits on the bottom of the pan.
Simmer mixture for 2 to 3 minutes, whisking every so often.
Adjust the thickness of the gravy. If it is too thin, simmer, whisking often until the gravy is as thick as you want it. If it is too thick, whisk in a little more stock.
Season the gravy with salt and pepper to taste.
Strain gravy if you want to get rid of any remaining encrusted bits you loosened earlier.
Pour gravy into a gravy boat and serve.