In a medium-sized bowl, combine the garlic, olive oil, parsley, oregano, red pepper flakes, sea salt, and black pepper. Mix until everything is well-combined.
Place the skirt steak in a large resealable plastic bag. Pour the chimichurri sauce over the steak, and seal the bag. Massage the steak to make sure the marinade is coating it evenly. Refrigerate for at least 2 hours, or overnight
Preheat the grill to medium-high heat.
Remove the steak from the marinade, and discard the marinade. Grill the steak for about 5 minutes per side, or until cooked to your desired doneness.
Let the steak rest for a few minutes before slicing. Serve with additional chimichurri sauce, if desired.