This is drill #3 in my swim book-Simple Swims:practices for balanced, stable swimming
Start in the Front Float with a gentle flutter kick. Gentle exhale. Shift the weight of the body to the left side (low side), then to the right as you gently kick the legs. Keep the arms straight but sloping down. Gently kick as you practice shifting the weight of your body from right side to left side, back and forth, turn the hips slightly and slowly. Keep the hips at the surface.