For those with a Nintendo Switch, I just dangled the wristband thing that connects to the JoyCon off of a table wrapped around the Xbox Thumbstick in Manual position. Worked perfectly. For those without a Switch, a piece of string with a small weight (empty soda can, heavier pen or marker) may work as well.
Manuals don’t count towards the achievement until they are landed. Just Ollie out instead of potentially messing up a flip trick out and ruining your progress.