To make the chimichurri sauce: In a mortar and pestle or food processor, mash or mince the garlic. Add the cilantro, parsley, thyme, and oregano and continue mashing until the herbs are coarsely ground. Mash in the red pepper flakes, then the lemon zest and vinegar. Slowly drizzle in the oil while mixing. Season the chimichurri sauce to taste with salt and pepper.