Make the Biscuits:
Preheat oven to 400°F (200°C). In a large bowl, combine flour, baking powder, salt, and baking soda. Cut in cold butter with a pastry cutter or fork until the mixture resembles coarse crumbs. Pour in the buttermilk and stir until just combined. If the dough seems dry, add a little more buttermilk.
Turn dough onto a floured surface, gently knead, and pat into a ¾-inch thick rectangle. Fold the dough over itself a few times, then pat out again and cut into biscuits using a round cutter. Place biscuits on a baking sheet and bake for 15–18 minutes until golden brown.

Make the Gravy:
In a large skillet over medium heat, brown the sausage, breaking it up as it cooks. Once fully cooked and browned, sprinkle in the flour and stir to coat the sausage. Cook for 1–2 minutes to eliminate the raw flour taste.
Slowly pour in the milk, stirring constantly. Let the gravy simmer until thickened, about 5–7 minutes. Season with seasoned salt and plenty of black pepper to taste.

Serve:
Split the warm biscuits in half and spoon the hot sausage gravy over the top. Serve immediately.