The recipe for this is open to many variations, depending on custom and individual taste. What I'm saying, is don't expect much in the way of precise amounts or hand-holding.
For enough gravy to serve 4 to 6 people, you'll need about 8 tablespoons of meat drippings, either from cooking off a pound of Country Sausage, augmented, if necessary, with some bacon fat or butter. Lately I've been using a little butter, with good results. Set the crumbled, cooked Country Sausage aside while you do the roux.
Heat the fat in a large skillet (iron if possible) while slowly heating a quart/liter of milk in a separate pot.
Sprinkle in the flour and mash it around to get a nice paste. Cook slowly until it's bubbly, about 5 minutes, and remove from the heat. (It won't look too nice.)
Add the roux to the pot of heated milk by tablespoonsful, whisking continually. Use all the roux. Keep some milk on hand in case this gets too thick.
You must stir or whisk nearly constantly.(You can do this while the biscuits are baking.) Keep the heat fairly low, just under medium, and it will gradually thicken. Do not allow it to boil.
Add the cooked, crumbled sausage meat, stir and heat a few minutes.
Taste for seasoning. Now, after the highly seasoned sausage has been added to the gravy, is the right time to adjust for salt and pepper. Customarily, it's well peppered.
Serve hot, in a gravy bowl, and let your guests dip their own to ladle onto split, hot biscuits. If serving just for yourself, skip the gravy bowl and just dish it up as you like.
Here's an image from another website.
It's the best B & G image I've found in my brief search. May yours look as good.