This is drill #5 in my swim book- Simple Swims: practices for balanced, stable swimming.
Start in the front float with a flutter kick. Simultaneously shift your weight to the left side, at approximately a 45° tilt. Keep the left arm forward, as the right hand comes to the front of the right thigh, belly turns to the right. Balance here with the flutter kick. It is easier to balance while tilted with the flutter kick. You do not want to be completely on your side. Stop, stand up, get a breath then do the right side