Think of hangetsu stance as a zenkutsu dachi done in such a way as to protect the groin area. Rather than thinking turn the toes in, or point the knees in think of it as closing the groin area. And when the floor is very slippery as often happens on a hot day when everyone is sweating buckets see how much less you slide when moving in zenkutsu dachi as compared to hangetsu dachi.