Float flat with arms parallel to each other, legs long, toes pointed, legs together. Fill your lungs with air, push your lungs down in the water, engage your low back to suspend your legs, and raise arms out of the water high enough to get heels to break the surface. Bonus if hips break the surface as well. Floating flat via pushing the lungs down teaches a swimmer that they don’t have to kick a ton to keep the legs near the surface, and that our bodies naturally want to float so long as we engage our core muscles enough to hold the right body position. Even if your feet slowly sink it’s OK. Your goal is to reduce the rate that your feet sink to the bottom. You will always kick a little while you swim and that will take care of getting your feet the rest of the way to the surface.