Add the oil, vinegar, cilantro/parsley, chili powder, garlic powder, dried oregano, ground cumin, salt, pepper, optional red pepper flakes, and chicken to a gallon-sized freezer bag. Seal and squish around to make sure the chicken is covered in marinade and everything is combined. (Freezing instructions begin here.)

Place the bag in the refrigerator for at least 2 hours and up to 24 hours.

Cook the chicken using one of these methods. The chicken is done when it reaches 165°F internally and/or is no longer pink inside.

Slow Cooker: Place chicken and marinade in slow cooker. Cover and cook on LOW for 2 ½ to 3 ½ hours. Really! That’s all it takes to get it done, otherwise, you’ll overcook and dry it out.

Instant Pot: Place chicken, marinade, and ⅓ cup chicken broth in a 6-quart Instant Pot. (Note: If using an 8 quart, add an additional ½ cup of broth.) Lock and seal the lid. Cook at high pressure for 7 minutes and use a quick release of the pressure when the cook time is up. (Note: It will take 10-15 minutes to come to pressure before the cook time starts.)

Grill: *Before marinating, pound out the chicken to about ¾ inch thick (or cut it in half lengthwise) to help with fast and even cooking. To do this, place one breast at a time inside a freezer bag and pound with the flat side of a meat mallet. Preheat grill to medium-high heat (400-450°F) and clean the grates well. Grill for about 4-6 minutes per side, closing the lid in between flipping, until done. The cook time may be longer depending on the thickness.