Begin by heating the oven as directed on the biscuit packaging—commonly to 375°F (190°C). Place biscuits on a baking tray and bake until puffed and golden, typically for 12 to 15 minutes. If preparing from scratch, start with biscuit preparation.
Place a large skillet over medium heat. Break the sausage into small pieces and sauté until fully browned and cooked through, around 7 to 8 minutes. Retain roughly 2 tablespoons of the rendered fat in the skillet to enhance the flavor of the gravy.
Sprinkle the flour evenly over the browned sausage. Stir thoroughly to combine and let the mixture cook for 1 to 2 minutes to eliminate the raw flour taste.
Gradually incorporate the warmed milk into the pan, stirring constantly to maintain a smooth consistency. Let the gravy simmer and thicken, which should take approximately 5 to 7 minutes.
Stir in salt and black pepper, adjusting to taste. Add optional seasonings—garlic powder and crushed red pepper flakes—if using, and mix until well blended.
Slice the freshly baked biscuits in half and spoon the hot sausage gravy generously over the top. Serve while warm.