Grease a medium casserole dish (I used a 10-inch round casserole dish). Preheat oven to 400 degrees.
Cut biscuits into quarters. Layer half of the biscuit quarters in the bottom of your greased casserole dish. Bake for 10 minutes.
While biscuits are baking, prepare the sausage and gravy. In a large skillet brown the sausage over medium-high heat until fully cooked. Sprinkle with flour and stir for 3-5 minutes until sausage absorbs the flour. Add milk, salt and pepper, and stir until mixture comes to a boil. Taste, add salt or pepper as needed to taste. (Add a bit of milk to thin the gravy if it's too thick at this point - it should be runny and not too thick)
Pour sausage gravy over baked biscuits. Top with remaining raw biscuit quarters and bake for 20-25 minutes longer until top layer of biscuits are golden and flaky. Serve immediately.