Focaccia

Hi everybody, I am making focaccia with Jeffrey Hamelman's Bread 2nd edition, and it says use Ciabatta with stiff biga for the focaccia, I followed all the directions, bulk fermentation takes 3 hours and final fermentation is 1 1/2 hours, but dough doesn't have enough volume and small bubbles on top, after baking it's thin, what can be the problem? thanks