A few of my fav’s to use with clients are:
V-UPS-Have client lie flat with arms overhead, they will then fold their body into a v where the hands and feet touch at the midline.
Pike up on the stability ball
Suitcase cruches- client crunches up and folds knees into chest
Windshield Wipers: Client lies flat and brings legs up to 45 degree’s or just high enough to where the back doesn’t arch. this can be done bent leg at 90 degree’s as well. then have them move legs from side to side while keeping the Torso flat on the mat.