Crumble the yeast in a small bowl then add the sugar and about 1/4 cup of lukewarm water from the 1-1/2 cups. Mix well with a teaspoon until the yeast melts.
Mix the salt with the remaining water.
Put the flour in a large bowl (or better in a mixer) then add the yeast mixture, extra virgin olive oil and salted water. Mix the ingredients very well until the dough becomes smooth, elastic and a little bit sticky. If the dough is too sticky to work with, add more flour until you have a ball. Just remember that the less flour there is, the better it will be because the focaccia might come out dry.
Take away the dough from the bowl, sprinkle some flour at the bottom of the bowl then put back the dough in the bowl. Cover with a clean cloth and let it rest in a warm, draft-free place for 2 hours or until the volume of the dough rises to twice its size.
After the dough rises, transfer it on a well-oiled baking pan then flatten it with your hands. The thickness should arrive at about 1 centimeter or thinner if you prefer.
Once flattened, make holes all over the dough by plunging all your fingers on it then prick it with a fork. Now you are ready to put the toppings.
Preheat the oven to 425 degrees F.
Distribute the sun-dried tomatoes, olives and thyme on the focaccia. Push them lightly in the dough then drizzle with extra virgin olive oil.
Let it rise again in a warm, draft-free place for half an hour.
Bake in the oven for 15 minutes in the middle rack.
After 15 minutes, take out the focaccia from the oven then sprinkle the mozzarella on top. Bake for 5 minutes more or until the mozzarella melts.
Drizzle with extra virgin olive oil before serving.