Preheat oven to 500–525°F. Grease the cast iron skillet generously with shortening.
Add flour to a large bowl. Build a wide, shallow well in the center — the bird's nest.
Drop 2 scoops of shortening into the well. Add a small pour of cold buttermilk.
Mix gently from the center out in circles, slowly pulling flour inward. Add buttermilk bit by bit. Keep the outer ring dry. Mix until a soft, slightly tacky dough forms. Stop as soon as it holds together.
Turn onto a floured surface. Press lightly with your palm — no kneading. Cut rounds straight down without twisting.
Place biscuits in the skillet with sides touching. Bake 12–15 minutes until golden brown on top.
Brush with melted butter immediately out of the oven. Serve hot.