With a mortar and pestle, or by hand, crush thyme and rosemary. Transfer herbs to a small bowl and stir in peppercorns and coriander seeds.
In a 1-pint jar, carefully place 3 cheese halves and sprinkle with half of herb mixture. Add remaining cheese and sprinkle with remaining herb mixture. Add enough oil to cover cheese completely and slide bay leaves down opposite sides of the jar. Cover jar tightly and chill, covered (4 days).
Let mixture come just to room temperature and preheat broiler.
Top each bread slice with a tomato and a marinated cheese half and arrange on a baking sheet. Broil about 4 inches from heat until cheese is golden, about 3 minutes.