Look Mayweather in the video above. First right punch, at the moment of the impact, only the toe is on the ground. The base still seems to me a bit more important in WC than boxing. Perhaps I am wrong...
No, its just that the base at that moment was the lead leg. Where many martial arts tend to keep both heels on the ground and the weight relatively evenly spread between between the two legs, boxing typically lifts one heel on impact for rotary force with the majority of the weight shifted to one leg. But there is still a solid base.