Simple core exercises are really good like a table top legs lower one and hold for 5 sec raise slowly lower opposite and hold etc repeat for 2 min sets. Roll down and roll ups. Going to half and holding. Slowly lowering until you feel you can no longer hold it and hold then back up to seated position repeat.
sit down with legs flat on floor (hold feet up maybe 6 inches off floor for more advanced workout). Get a weighted ball/kettlebell/dumbell, keep looking forward while touching weight on floor each side with both hands holding the weight. 6 of each side x3
lie on floor and raise leg, keeping both legs straight, up as high as you can (90degrees+) for 12rep x3 - (stop feet from touching floor for more advanced workout)