I wouldn't recommend using this method as it has a larger margin of error than the non-cross method which is also available on this website.

Basically the idea is that you keep the finger that held the middle flick completely stationary and instead cross over the opposite hand, using the same flick join line that the game provides you and hit the pattern in that manner, except you use the crossed hand to hit all 4 flicks instead of just 2 in one fluid motion. (it's easier) Just be sure to not accidentally lift the hold hand until you're absolutely sure all 4 flicks have been hit properly as premature release will kill your combo more often and easily than you think.