Try this core strengthening exercise that involves doing a traditional crunches on a BOSU, this adds an instability factor that enhances your ab-sculpting results.
1. Lie face-up on BOSU, flat side down, with back on center of dome, knees bent, feet flat on floor in front of you.
2. Place hands behind head, elbows out to sides, and crunch up with upper body until you feel resistance; lower.