Not using a poolish starter

Fermentation develops flavor, so it is reasonable to expect that dough with a longer fermentation window will be more flavorful than dough that has been rushed through the proofing and fermentation process. You should make a poolish starter for more flavorful focaccia. A poolish starter, as opposed to a levain made from wild yeast, is made from commercial yeast that has been allowed to pre-ferment for 12-24 hours before being mixed in with the rest of the bread ingredients. You won't get the same strong, acidic flavor as a levanin, and you won't have to go through the arduous process of keeping your sourdough alive and fed until you use it.

According to The Weekend Bakery, a poolish starter can be made simply by combining equal parts flour and water (resulting in 100% hydration). The amount of instant yeast you'll use depends on how much time you have to allow the dough to pre-ferment; for a culture that will be used in eight hours, you'll use more yeast than one that will take a day to pre-ferment. The yeast percentage for an eight-hour pre-ferment range between 0.23 and 0.33% of the flour weight.