What stomach problems do you have? Complex health issues have complex roots and consequences, from the elements up to just a little bad energy circulation.
You can do whatever feels easier for you, and you have the conviction that is working. On the organs, I like to use my hands. Make your hands full of energy and apply it by touching the afflicted area. This can be done also with foundation meditation. Have a good affirmation with positive conditioning and do it for a lot of time, even after the health issue was healed. Have the conviction that you are healthy and you inhale healing energy.
You can do all the variations of the foundation meditation in one working.