Cut the cold butter into 1/8-inch-thick slices; refrigerate until you're ready to make the dough.
Whisk together the flour, salt, baking powder and baking soda in a mixing bowl, and refrigerate that, as well. Position a rack in the upper third of the oven; preheat to 425 degrees. Lightly grease a rimmed baking sheet, or line it with parchment paper or a silicone liner.
Add the cold butter pieces to the chilled dry ingredients, tossing them until they are evenly coated. Press the butter pieces between your thumbs and forefingers into small flat pieces, or "leaves." (Some pieces as big as a quarter are OK.) Add the buttermilk, as needed, and mix gently until just combined. The dough should be barely cohesive; don't worry if there are dry bits, because they will be incorporated as you pat and fold the dough.
Lightly flour your work surface. Transfer the dough there, patting it into a 3/4-inch-thick rectangle. Fold the dough in thirds as you would a letter, bringing one-third in over the middle third, followed by the final third over the other two. Gently roll or pat the dough into another rectangle. Repeat this fold-and-roll process once more if the dough isn't cohesive or if you want to create more layers.
Lightly flour the top of the dough. Use the 2-inch cutter to create 10 to 12 rounds of dough, being careful to cut straight down and not twist the cutter (to ensure the biscuits get the best rise). You can reroll the dough once, though you might not get the same rise. Or use the bench scraper or a sharp chef's knife to square the sides and edges of the dough rectangle, then cut 8 to 10 squares or rectangles. Place the biscuits on the baking sheet, spacing them about 2 inches apart.
