Dead easy. Best fresh; they don't keep long or well.
2 cups unbleached all-purpose flour
1 tbsp double-acting baking powder (they're pretty much all double-acting these days, apparently)
1 tbsp sugar; could probably use less
1 tsp salt
½ tsp baking soda
4 tbsp cold unsalted butter cut into ¼-inch cubes
1½ cups cold buttermilk, preferably low-fat
for forming biscuits:
approx 1 cup flour spread over a rimmed baking sheet
Preheat oven to 500°F.
Spray a 9-inch round cake pan with nonstick cooking spray; also spray inside and outside of a ¼-cup measuring cup.
Pulse dry ingredients in food processor to combine. Scatter butter cubes over and pulse again (about 10 times) to form a crumby mix.
Transfer to a bowl and add buttermilk; stir with a rubber spatula until just combined. It will be lumpy and sticky; don't worry.
Scoop out biscuits with the sprayed measuring cup and drop them into the floured baking sheet. with your fingers, roll them a little so they are lightly but evenly coated; form gently into rounds; shake off excess flour; and arrange in cake pan, about 9 around the outside and 3 in the middle. It's OK for them to be lightly touching or even smushed hard against each other; and it's OK if it comes out as less than 12. The mixture may start sticking to the cup, in which case scrape it out with a spoon; don't worry, it'll all work out OK.
Bake 5 minutes at 500°F then reduce heat to 450°F and bake another 15 minutes until golden brown. They will have spread and merged together, but the flour coating means they will break apart again easily.
Remove from oven and cool in pan 2 minutes; invert onto a clean kitchen towel and then back onto a plate; break apart; cool 5 minutes covered with the towel.