1. While standing, take a deep breath in and hold it. In this state, contract your abdominal wall as though you are trying to shrink your tummy as much as possible and hold this state for a few seconds. Then exhale fully and let your tummy relax. Repeat this cycle five times.
2. While lying down, take a deep breath in and hold it. In this state, use the pads of your fingers of both hands to gently but firmly massage (with doTERRA DigestZen Digestive Blend, optional) your abdomen from the bottom border of your rib cage all the way down to the top border of your pelvis - put another way, through the entire length of your abdomen. Exhale fully. Repeat this cycle five times.
These two exercises promote healthy flow of stools through your colon and encourage optimal waves of contraction through the smooth muscles that line your colon. In the absence of pain or inflammation, one can use a good amount of firm pressure with this massaging technique, pressing a good inch or two into the abdomen. Where there is pain or inflammation, it's best not to massage the area without first consulting with one's physician.
As an interesting side note, the first technique described above typically leads to a long term decrease in circumference measured around all sections of the abdomen, most noticeably around the level of the belly button. This is most likely due to improvement in tone and strength through the transversus abdominis muscle, the deepest layer of muscle that surrounds your abdominal cavity. To the best of my knowledge and experience, no other exercises condition the transversus abdominis more effectively than the "inhale and contract" method described above. Most conventional core exercises like crunches, leg raises, and plank mostly target the more superficial layers of abdominal muscle, including the rectus abdominis and obliques.