Use a turkey baster to put only the fat (top layer) in the pot
Let fat heat up and add a bit of flour until it becomes a paste
Add rest of fat and drippings. Alternatively add starch water from boiled potatoes if present.
Turn heat down a bit and mix
Optionally, preheat some cream (1/4 cup, 35%) to add for creaminess. Make sure it’s preheated so there is no temperate shock in either direction or risk of curdling when added.