Also, since Ice Slick will knock the person prone, whether moving or not and even if their check fails by only 1-4, it obviously doesn't follow normal balance rules. So, why should the DC? It's a 1st level spell, so the save DC should be in the 14-16 range early on, and increases as the caster's ability score does. Is that too powerful that it needs to be nerfed to 10, especially since there's only one check per round, unlike Grease's Reflex plus balance?