Dissolve yeast in water in a large bowl; let stand 5 minutes.
Lightly spoon flour into dry measuring cups; level with a knife. Add 1 cup flour to yeast mixture, stirring well to combine. Cover and let stand at room temperature 8 hours or overnight to create a sponge (mixture will become very bubbly).
Preheat oven to 350°.
Remove papery skin from garlic head (do not peel or separate cloves). Wrap in foil. Bake at 350° for 1 hour; cool 10 minutes.
Separate cloves; squeeze to extract garlic pulp. Discard skins. Place garlic pulp, 1 tablespoon oil, and 1 teaspoon salt in a small bowl, and mash with a fork until smooth. Stir into sponge.
Add 2 cups flour to the sponge; stir until a soft dough forms. Turn dough out onto a floured surface. Knead until smooth and elastic (about 8 minutes); add enough of remaining flour, 1 tablespoon at a time, to prevent dough from sticking to hands (dough will feel tacky).
Place dough in a large bowl coated with cooking spray, turning to coat top. Cover and let rise in a warm place (85°), free from drafts, 45 minutes or until doubled in size. (Gently press 2 fingers into dough. If indentation remains, dough has risen enough.)
Punch dough down. Cover and let rest 5 minutes. Divide dough in half; roll each half into a 10-inch round.
Place 1 dough round on a baking sheet sprinkled with cornmeal. Arrange basil over dough, leaving a 1/4-inch border; top with bell peppers. Sprinkle evenly with cheese. Top with other dough round; pinch edges to seal. Lightly coat with cooking spray. Cover and let rise 45 minutes or until dough is doubled in size.
Preheat oven to 400°.
Uncover dough. Make indentations in top of dough with a knife. Gently brush dough with 1 1/2 teaspoons oil, and sprinkle with 1/4 teaspoon salt. Bake at 400° for 30 minutes or until the focaccia is browned on bottom and sounds hollow when tapped. Remove from pan; cool on a wire rack.
I have never worked with bread dough before or yeast and it was really easy to make. The results while not beautiful due to my amateur skills turned out delicious! You need a whole day for this recipe though, there are lot of rising steps.