Dissolve the baking soda in the vinegar. It needs to bubble.
Sift the flour. Make a well in it. To it add the salt, sugar, oil and vinegar with baking soda. Pour in a little water too.
Knead everything very well. Let it rise for 30-40 min.
Bake in a preheated 356°F (180 °C) for at least 30 min.