It is best to marinate thawed chicken but if it is still frozen, here is my ultimate recipe for doing it. You want to make sure you get the most flavor into the chicken while marinating. This method known as the Marinate Twice Recipe has worked best with all my personal chef experience & now you can do it at home too.
Place frozen chicken pieces in a marinading container with a lid. If you do not have one, a large baking pan that has a tall rim will do. Try and separate any pieces that you can so they are not sticking.
Pour ½ of the marinade over the chicken pieces. Rotate and flip them over so both sides have a bit of marinade on them.
Snap the lid on, if you have one. Otherwise, cover with plastic wrap or foil. Place the container of chicken & marinade in the refrigerator. Reserve the rest of the marinade in the refrigerator as well.
Let the chicken defrost while in the marinade for 12 - 24 hours. It will depend on how large the chicken pieces are.
Once the chicken is about 80% defrosted, drain off the juices and the marinade that is in the container or dish. Add the remaining ½ of the marinade. Let the chicken sit in the marinade for the remaining hours until the chicken is completely thawed out and ready to cook.
When ready to cook, remove the chicken from the marinade. Discard the marinade. Grill, smoke, bake, or saute your chicken as desired.