Pour turkey pan drippings into a glass measuring cup and allow the fat to rise to the top.

Skim 1/4 cup of the fat and place it into a medium saucepan over medium heat; supplement with unsalted butter if drippings are insufficient.

Whisk the all-purpose flour into the hot fat to create a roux and cook for 2 minutes until golden and fragrant.

Gradually pour in the turkey stock while whisking constantly to ensure a smooth, lump-free consistency.

Stir in the remaining concentrated pan juices (the liquid below the fat layer).

Bring the gravy to a gentle boil, then reduce heat and simmer for 5 to 7 minutes until thickened to the desired consistency.

Add salt, pepper, and minced sage to the mixture.

Strain through a fine-mesh sieve if a perfectly smooth texture is desired, then serve immediately.