Preheat oven to 400 degrees.
Lightly grease a 9 x 9 inch pan with cooking spray, set aside.
Open biscuits and cut each biscuit into 4 pieces.
Layer half of the cut biscuits in your prepared pan.
Bake for 10 minutes.
While it bakes, brown the sausage in a skillet over medium high heat until fully cooked, then drain grease well.
Add flour to the cooked sausage and mix until all is covered.
Lower heat to medium, and cook flour/sausage mixture for 3-5 minutes, stirring frequently.
Add milk, salt, and pepper and stir to combine until it comes to a slight boil.
If the gravy is too thick, add a bit more milk. You want the gravy to be thickened but not too thick.
Pour the sausage gravy over the cooked biscuits.
Layer the remaining uncooked, quartered biscuits over the gravy.
Place casserole dish on a baking sheet, and bake for 20-25 minutes or until golden brown.
If they start to get too brown, you can cover with foil for the last 10 minutes.