Achieving this kind of movement while moving at such high speeds was almost impossible for someone with Leroy's physique and mana control.
However, he had decided to sacrifice quite a bit to be able to surpass what someone at his level would be able to do.
By sacrificing his sense of control and using a predetermined path that he couldn't change after he had started the movement as well as sacrificing his sense of balance for a few moments after finishing the maneuver he was able to accomplish something like this.
That didn't mean that it was easily achievable however as one still had to focus all the mana in their legs as the calves of their feet for a moment and then forcefully keep that mana in the same spot until the last moment where they forcefully released it and redirected it towards other muscles which allowed him toke take that quick sidestep.