Heat the oven to 400°F. Combine the flour, baking powder, baking soda, and salt in a large bowl. Add buttermilk and oil. Stir to combine. Turn out onto a clean work surface and knead a few times until it holds together. Shape into a ball and place in a skillet or on a baking sheet. Slice a deep cross into the loaf. Bake until brown and an instant read digital thermometer reads 200°-205°F. Remove the loaf to a rack to cool slightly, at least 10 minutes before slicing. When ready to serve slice into pieces with a serrated knife. Store in a sealable airtight container for up to 4 days.