In a medium sized mortar add peppercorns and coriander seeds. Crush with pestle to a medium sized grind. Empty seeds into a small bowl and clean out the mortar and pestle with a paper towel.
Add garlic and salt to mortar and crush into a fine paste. Place into bowl with the ground pepper and coriander. Slowly drizzle in half of the oil. Mixture should be a loose paste but not runny. If it is still too thick, add a little more. Stir in the rosemary and thyme. Let mixture sit for a few minutes, and stir once again before applying generously to both sides of the steak. Cook as directed.
If you are planning to marinate the steak, omit the salt from the rub, and season the steak with it right before cooking.