Add buttermilk mixture to dry ingredients and stir with a rubber spatula just until all flour is incorporated and batter pulls away from sides of the bowl. The dough should be stiff and not super wet. If the dough is wet, add more flour 1 tablespoon at a time, stirring to combine, until fairly stiff.
Generously flour a work surface. Dump biscuit dough from bowl onto prepared work surface and turn to coat all surfaces with flour. Knead on counter 5-6 times (about 30 seconds). Flip over on the work surface to coat with flour then pat into a 6-inch square. It should be a 1/2-2-inches in height.
Cut four biscuits with a 2 1/2-inch biscuit cutter. Place biscuits on the prepared sheet pan. Knead scraps a few times till they hold together, then pat into a small rectangle and cut two more biscuits. Transfer last two biscuits to the sheet pan, spacing about 1 1/2 inches apart. (See Café Tips in the post for an even easier cutting technique).
Place in oven and bake until tops are golden brown and crisp, 8 to 18 minutes. (start checking them after 8 minutes as ovens vary. You want them to be a nice golden brown, but not too brown - check the pictures above for correct color.)
Recipe adapted from Cooks Illustrated via Serious Eats