You slide the board over to the man, but he is not very coordinated and he trips over the board.
That is still enough for the magic to take effect, though! As the man falls, he lands on the skateboard, his expanding butt absorbing the impact.
Instead of getting up, his body shrinks and transforms atop the magic board. His jeans become a pair of tight women's shorts as breasts form underneath his black undershirt. Long hair bursts from his scalp as you see his face begin to change to a new feminine look.
The newly transformed girl continues to sit on the skateboard, throwing her arms up as she scoots along sitting down.