There are a lot of different exercises for flattening the stomach that are as good as crunches and maybe even better!
Here are some exercises for flattening the stomach without doing crunches:
1. Abdominal twist with weights
First, lay on the floor. Lift your body and both legs off the floor, like V shape. Grab a 5-pound dumbbell or a medicine ball, cross your legs and swivel your upper body left to right. Keep your stomach muscles tight during the routine.
2. Plank with a twist
First, get on the floor and do the usual planking position. Twist your hips slowly from left to right, and make sure that your upper body, supported by elbows and forearms, remains still. While doing a twist, exhale to really zap the belly flab.
3. Donkey kicks
First, get on all fours. Tuck your toes under and keep the back neutral. While contracting the stomach muscles, take your knees a couple of inches off the floor. Then, bring the right knee close to the chin, and strengthen it behind you to do a kick. Repeat for 8 times and then do the same on the other leg. Clench your butt muscles, while doing a kick.