The Infinity Punch is depicted as being thrown in one of two ways, both while Hawk is swaying backward. Either Hawk throws an uppercut from his swayed back position, or an overhand. Hooks are also possible from this position, but he has not preformed one on screen. He presumably swings his upper torso to the side to close the distance for these punches. All the punches are aimed at the opponent's head, though it would not be difficult for him to aim for the body.
Hawk's incredible flexibility and athleticism are what allow him to perform this punch.
Strengths & WeaknessesEdit
The Infinity Punch is named because it can be thrown at and from any angle. The sheer awkwardness of the angle Hawk throws it at while swaying almost certainly will catch the opponent off guard, and it seems Hawk can throw them with the speed of regular jabs, straights, and so on.
However, the sway-around angle is the only angle at which Hawk attempts to throw an Infinity Punch, which renders him vulnerable to falling over from any marginally powerful jab, as Takamura showed during their match. Should Hawk become incapable of swaying for whatever reason, he must revert to throwing punches standing up.