Prepare the dough:
In a bowl, mix the yeast with the warm water and sugar. Let it rest for 5-10 minutes until bubbling.
In another large bowl, combine the flour and salt. Make a well in the centre and pour in the yeast mixture and olive oil.
Knead for 10 minutes by hand (or 5 minutes in a stand mixer) until you have a smooth, elastic dough.
Shape into a ball, place in a lightly oiled bowl and cover with a damp cloth. Let rest in a warm place for 1 hour, or until doubled in size.
Make the topping:
Mix the olive oil with the chopped garlic, rosemary and thyme. Set aside.
Shape and decorate the focaccia:

Preheat the oven to 220°C (430°F).
Lightly oil a baking sheet or line it with baking paper.
Spread the dough out on the sheet with your hands, forming a rectangle or circle about 2 cm thick.
Using your fingers, gently press into the surface to create small indentations.
Brush the top with the oil and herb mixture.
Sprinkle with crumbled feta cheese, coarse salt, pepper and, if desired, add olives.