Try the SLT way to tone your obliques.

1. Sit sideways on the platform of the Megaformer (or use a bench instead), resting on the bottom thigh, bottom leg bent with the foot underneath the top knee. 
2. Keep the top leg straight with the foot under the "X" strap (or sub something stable such as slipping your foot beneath the bed or using a workout buddy to hold onto it). 
3. Place your hands behind your head, elbows pointing away from the body, and fold over sideways, away from the bottom foot, creating an elongated side crunch.
4. Use your obliques to pull your upper body straight to the ceiling, pulling from the rib cage.

Source: SLT