This nothing less than boring stepping backwards drill. I have yet to see someone who can naturally step backwards under his hip.
Any exercise need to be integrated into a dancing context.
Tough, tough, tough! Very few dancers, even among those known as the best, can keep the scapula in place, engage the minimal muscles, losen the arm and keep a smooth connexion during the lollie's kicks. Initiate inside and outside turns WITHOUT extra pump or prep is in the hardest techniques to master. Better start working on it now!
Choose a simple theme, here: kick ball change on 5 & 6 in a regular throw out. Keep that going and see what you can come up with.