Your left foot is flat on the floor when you throw a right hand; it should not pivot. The weight ends up on the left foot when you throw a right uppercut; no pivoting here either. For the left uppercut,the wt begins on the left foot which,at the end, has the heel lifted a bit. When throwing a left hook the left leg pivots to the right on the let toe. I've been posting apunch by punch breakdown that is much more detailed.