Hi Jacy! I'm definitely no "expert", but here's an exercise I used to do for my waist, and it seemed to help tone and slim quite alot!

Stand with your feet planted at hip distance apart, knees slightly bent. Tuck your pelvis forward firmly to stabilize your lower back. Keep your arms close to your sides, with elbows bent up. Then begin twisting your upper body only from side to side, as far as you can (like you were turning to look behind you), back and forth, back and forth. But do it gently, so you don't wrench your back!

Hope this helps!