The varial kickflip used to be called the ’180 shove-it kickflip’ since it’s basically a combination of the straight kickflip and the basic pop shove-it, but ‘varial’ obviously sounds cooler, so we’ll run with that.
Put your feet in the position you do a kickflip.
You’re going to do the Shove-It motion with your back foot and the flip motion with your front foot.
Pop it, shove it, flip it, wait for it to do a 180 on the flip. While it’s going around, see your grip tape, catch it, land it, and roll away.