Left Foot in the "Floating Double Bass" Technique

My left leg is horrid at this technique. I still end up using more of my leg instead of the ankle. I've also noticed my left foot does a sweeping motion when I attempt this technique, but I have no idea if this actually affects my ability at this.



Any tips or ways to practice this technique for my left leg and in general?

Left Foot in the "Floating Double Bass" Technique