Stir baking soda into buttermilk and set aside. If the mixture bubbles, the baking soda is still good. If it doesn’t bubble, you need to buy more.
Place both types flour and salt in a large mixing bowl and stir.
Make a well in the center and pour in buttermilk and soda. Stir until the flour is wet.
Turn out onto a floured surface. Sprinkle with flour. Knead gently and add more flour as necessary until the dough is no longer sticky. Form into a ball and place on baking sheet that has been sprayed with non-stick spray or is covered with a baking mat.
Using hands, press out the dough in a circle that is 1 ½ inches thick.
Using a sharp knife, make an X one quarter inch deep in the top of the dough. Lightly brush top with cooking oil.
Bake in a preheated 425 degree oven for 25 minutes; reduce heat to 350 degrees for an additional 15 minutes.
Cool on a baking rack. For best results, the loaf shouldn’t be cut for 6 hours. Best of luck trying to wait that long.