Preheat oven to 450F.
In the bowl of a food processor, add the flour, salt, baking powder and baking soda. Pulse a few times to combine.
Sprinkle the butter pieces over the top of the flour mixture. Pulse until pea sized crumbs form. Slowly pour the buttermilk in with the machine running. Dough should be pretty sticky.
Flour a countertop surface with additional flour. Turn out the dough and sprinkle flour over the top. Knead a few times, adding more flour as necessary, until the dough is no longer sticky.
Roll out the dough to about 1/2" thick. Do a letter fold and fold in thirds. Fold in half lengthwise, short end to short end. Gently press out to 3/4" again.
Cut biscuits with desired size biscuit cutters and place on baking sheet or in cast iron skillet. Place them closer together for higher, softer biscuits, farther apart for shorter, crispier biscuits.
Brush biscuit tops with butter. Bake in preheated oven for 12-15 minutes.