Trim excess fat from flank steak and slice into 1/4-inch strips.

Whisk together garlic, ginger, fish sauce, soy sauce, lime juice, brown sugar, black pepper, and chili flakes.

Coat the flank steak strips with marinade and refrigerate for at least 30 minutes.

Heat a skillet over medium-high heat and add vegetable oil.

Sear steak strips in a single layer for 3-4 minutes per side.

Cover seared steak with foil and let it rest for 5 minutes.

Pour reserved marinade into the hot skillet and simmer for 2-3 minutes.

Slice rested flank steak against the grain and arrange on a platter.

Garnish with cilantro and serve with lime wedges.