I prefer getting students to learn the control of the tongue by exercising it (basic level stick the tongue out, the direct it up, down, left, right and repeat, then moving on to something like pushing the tongue into the bottom teeth then pushing up and out, then down and back). That way the student learns to control the tongue to lift when they want/need to and retract when they want/need to. I much prefer a slightly raised tongue on an ‘ee’ sound for example