In a mixing bowl, whisk together the orange juice, lime juice, soy sauce, minced garlic, cumin, oregano, black pepper, and salt to create the marinade.

Place the flank steak in a large resealable plastic bag and pour the marinade over it. Seal the bag and refrigerate for at least 1 hour, preferably overnight.

Preheat the grill to high heat.

Remove the steak from the marinade and discard the marinade.

Grill the steak for about 5 minutes on each side for medium-rare, or until desired doneness is reached.

Remove from the grill and let the steak rest for 5 minutes before slicing.

Slice the steak against the grain into thin strips.

Serve with chopped cilantro, diced onion, diced tomato, sliced avocado, and lime wedges on the side.