One piece at a time, put each piece into the Ziplock by itself, press out excess air, and seal it.
Use the rolling pin to pound the chicken piece until it's flattened to about 1/2 to 1/4 inch thick.
After each piece, remove from the bag and set it aside. Put a new piece in the bag and pound it flat. Do this for each piece one at a time.
Once all pieces are pounded flat, put them all back in the bag.
Add the lemon juice, pickle juice, salt, water, and any additional, recipe-specific spices.