Sit like a yogi.
First thing, you need to sit like a yogi in your office chair. Adjust your chair so that you sit with your legs a little more bent by lowering the chair and moving the back straight up so it allows you to key in your posture. Even just simply changing the position of your chair every hour will be beneficial. Yogis always sit straight up and are mindful of their posture and the position that they are sitting in. Just be sure that you are mindful of your posture.