All it takes is one civilization to shoot off their mouth and get destroyed by a much more advanced neighbor, in some way that doesn’t look quite natural. That will tend to confirm the cosmic paranoia.
Close. You don’t add liquid and flour. You brown the meat, and render out fat. It’s vital to have a couple tablespoons of liquid fat in the pan. If you don’t get enough from the sausage, augment with a bit of butter or oil. Heat around medium.
Then sprinkle in flour, about equal in volume to the liquid fat, and stir. You gently fry the flour in the oil to cook off the raw flour flavor. It’ll go from white to about sand color. If your proportions are right it will look a bit like wet sand, and will smell like roasted nuts a bit.
Now slowly stir in cold milk while whisking gently to mix and prevent lumps. Scrape the bottom to deglaze any browned on flecks of meat. You want to heat it to just bubbling not to scorch the milk. It’ll thicken up.
Then grind a bunch of pepper in to finish it off, and pour over biscuits, fried taters, or whatever.
All gravy works this way, pretty much. Gravy for turkey? Replace the milk with poultry stock. Gravy for steak? Beef stock it is.