Bake biscuits according to package directions.
Meanwhile, in a saucepan over medium-high heat, cook sausage while chopping it up into small pieces until browned and cooked through. (Do not drain excess fat from the sausage—it helps bring the flour and milk together.)
Once sausage is cooked through, carefully stir in flour ½ cup at a time until sausage has a nice coating.
Slowly add milk until you have reached your desired consistency. If you prefer a more runny gravy, add more milk. If you like the gravy to be thicker, add less milk. If you find you have added too much milk, add some flour to thicken it up.