Heat oven to 450° F and set the rack to the highest position (as long as it has at least 4 inches clearance).
Lightly flour a baking sheet. Set aside.
In a wide mixing bowl, sift together the flour, salt, baking soda and sugar. Then sift again.
Add the buttermilk and mix into the flour, working quickly (I use my hands).
Knead the dough gently. Not too much, so it doesn't toughen. Too little kneading and it won't rise enough.
Form a round loaf about 3-4 inches thick.
Use a floured knife to cut a cross in the top.
Immediately put into the preheated oven for 30 to 40 minutes.
The bread is done when tapping on the bottom with your knuckles sounds hollow.
Remove the loaf of bread from the oven and immediately wrap with a tea towel to prevent the crust from getting too hard.