What should i do at the gym to work on a flat stomach/abs?

Core: For a flat belly, you have to both tone muscles and reduce belly fat. The first is done with abdominal and oblique core work like sit ups and crunches. The latter s done with decreased calory diet and aerobic exercise.

Flat abs: For a flat abdomen eat healthfully ; be physically active. Calories burned must > calories consumed. To tighten ab's do crunches, reverse crunches, exercise ball crunches, pelvic thrusts, lying leg raises, side bridge ; “bicycling” exercise on your back. Engage in regular aerobic exercise (i.e., running, swimming, nordic track, bicycling, kickboxing, walking, cross country skiing, hiking, etc.).