Preheat oven to 350° Fahrenheit. Grease and 8x8 baking dish with cooking spray.
COOK
Use a large skillet to cook sausages over medium-high heat until brown. About 5 minutes. Sprinkle with flour and add milk. Bring to a boil.
Stir frequently. Reduce heat to medium and simmer until the sauce begins to thicken. About 1 minute.
ASSEMBLE
Spread the shredded hash browns on the bottom of the baking dish. Pour the sausage mixture over the hash browns. Top with green onions and shredded Cheddar cheese.