Flank and skirt steaks are flavorful cuts of beef, but they can become dry if overcooked due to their lean nature. However, with the right cooking techniques, you can ensure that flank or skirt steak remains juicy and tender. Here are some tips to cook flank or skirt steak so that it is not dry:

1. **Marinate**: Marinating the steak before cooking can help tenderize the meat and add flavor. Choose a marinade that contains acidic ingredients like vinegar, citrus juice, or yogurt, as well as herbs, spices, and olive oil. Marinate the steak for at least 30 minutes, or preferably overnight, in the refrigerator for maximum flavor and tenderness.

2. **Cook to Medium-Rare or Medium Doneness**: Flank and skirt steaks are best cooked to medium-rare or medium doneness to avoid becoming dry and tough. Overcooking can cause these lean cuts to lose moisture and become less tender. Use a meat thermometer to ensure that the internal temperature reaches around 130-135°F (54-57°C) for medium-rare or 140-145°F (60-63°C) for medium doneness.

3. **High Heat**: Cook flank or skirt steak over high heat for a short period to seal in juices and develop a flavorful crust on the outside. You can grill, pan-sear, or broil the steak for optimal results. Preheat your grill or skillet until it's hot before adding the steak.

4. **Resting Period**: After cooking, allow the steak to rest for a few minutes before slicing. This resting period allows the juices to redistribute throughout the meat, resulting in a juicier and more tender texture. Tent the steak loosely with foil to retain heat while resting.

5. **Slice Against the Grain**: When slicing flank or skirt steak, be sure to cut against the grain. Cutting against the grain breaks up the muscle fibers, resulting in more tender and easier-to-chew meat. Look for the direction of the muscle fibers and slice perpendicular to them.

6. **Thin Slices**: For flank or skirt steak, it's best to slice the meat thinly across the grain. Thin slices help ensure that each bite is tender and juicy, even if the steak is slightly cooked.

By following these tips, you can cook flank or skirt steak to perfection, ensuring that it remains juicy and flavorful without becoming dry. Experiment with different marinades and cooking techniques to find your preferred method for preparing these delicious cuts of beef.