Positioning yourself the proper way in the water is crucial. Start by floating and maintaining a face-down position while kicking. Keep your body streamlined while trying to propel forward. This position is called prone floating. If you want to learn how to float in the water in 6 easy steps, check out this article.
The flutter kicks are produced with both legs moving up and down one at a time. As you kick one leg up, you kick another down, and vice versa. Your hips are the driving force and help you to initiate the kicks. Your ankles work like propellers and create propulsion in the water.
Your flutter kick consists of 2 phases. There is an upward kick and the downward kick. Both phases are initiated with the hips and get the whole leg involved. Make sure to create propulsion while performing both the upward and the downward beats.
The downward phase of the kick is produced with the help of your quads and hip flexors. As your foot makes contact with the water during the downbeat, your ankle and foot will naturally extend, propelling you forward with each kick.