Focaccia is such a versatile flatbread. The dough recipe I am about to unveil here *drumroll please* is my well-tested recipe, adapted from a rosemary focaccia recipe I stumbled upon ages ago. I have incorporated my knowledge of yeast and their colonies acquired in first year biology class. Yeast colonies prosper in sugary and warm environment. And, salt kills the yeast, so it is always best to add the salt towards the end.
I recommend that you use bread flour and gluten to make focaccia. As the presence of gluten would give the bread more spongy and airy texture. But, if you do not have bread flour you can substitute it with equal amounts of all purpose flour, which has less gluten. You won't be compromising on the flavor. It is just the lesser gluten content will result in a flatter bread. In that case, I recommend you use a quarter sheet (9 x 13 inches) pan, instead of a half sheet (18 x 13 inches) pan, which I am using here. All purpose flour is more elastic and you would find it difficult to stretch out into a half sheet pan.
So let's get started.