I am forever doing somthing different in my classes to keep it interesting.
Using the stability ball, with a partner. Both are sitting on the ground facing each other. Toss the ball back & forth.
Cue: Abs tight, knees bent.
By yourself: use the wall! Toss & catch...same idea. Use soccer balls or basketballs if accessible.
Sitting on the ball: inhale, exhale flattening abs. Cue: Flatten ribs towards spine & exhale OUTWARD toward the side of the ribs.
Elbows bent, hands facing each other (like a prayer pose).
The partner stuff is always fun to watch. They always get mixed up then they laugh!
Make it fun. They'll appreciete the challenge!