In a large mixing bowl, whisk together soy sauce, honey, minced garlic, olive oil, rice vinegar, ground black pepper, and optional red pepper flakes until fully combined.

The marinade should have a fragrant, sticky consistency.

Place the skirt steak in a zip-top bag or shallow dish, and pour the marinade over it, ensuring the meat is well-coated.

Seal the bag, or cover the dish tightly, and refrigerate for at least 1 hour, ideally up to 6 hours.

Preheat your outdoor grill to medium-high heat, aiming for around 400°F (204°C).

Lightly grease the grates with vegetable oil to prevent sticking.

Carefully remove the skirt steak from the marinade, allowing excess liquid to drip off.

Place the steak on the grill and cook for 3-4 minutes on each side for medium-rare.

A minute before taking the steak off the grill, brush some reserved marinade onto the steak for an extra layer of flavor.

Transfer the steak to a cutting board and let it rest for about 5 minutes.

Once rested, slice the steak thinly against the grain.