Collect 2 cups liquid and strain out your pan drippings to collect anything floating around, then add to a sauce pan.
Turn heat to low and melt in butter.
Then vigorously whisk in the flour, being sure to not leave any lumps.
As the mixture heats, and comes to a low boil, it will begin to thicken.
Once thickened, remove from heat and add in salt and pepper to taste.
Enjoy!