Preheat the oven to 450°F.
Whisk together the flour, salt, baking powder, and baking soda in a large bowl.
Dump in the chilled butter and lard and rub them into the flour by pinching the chunks of fat. Stop when the mixture has a breadcrumb-like texture.
Add about half of the buttermilk and stir with your hand to start bringing the dough together. Pour in the rest of the buttermilk in one or two more additions, gently working the dough until all the flour and buttermilk are incorporated and a soft, sticky dough has formed.
Turn out the dough onto a floured surface, scraping out the bowl to get all the dough.
Sprinkle the top of the dough liberally with flour and roll the dough to ¾ inch thick.
Using a 2½" round biscuit cutter dipped in flour, cut out as many biscuits as you can from the first roll. Don't twist the cutter, as doing so will seal the sides together, inhibiting their rise.
Gently re-roll the scraps and cut more, being careful not to overwork the dough. Place the biscuits with their sides touching on the baking stone or cookie sheet. Let them rest at room temperature for 10 minutes for a higher rise.
Bake for 15-20 minutes at 450°F. They should be well risen and golden brown.