Dissolve the baking soda in the warm water and add it to the dough. If using a stand mixer, beat the batter for a minute or two. Or use an electric mixer to beat the batter. If some small lumps remain that's okay. Any remaining lumps will dissolve during the next resting stage.
Cover the batter and let it rest in a warm
place for at least 30 minutes (see note below). After 30 minutes the batter should be nice and bubbly.