Frostblink of Wintry Blast attack in (two) place(s) setting question

Hello there!
I am having trouble with my single target on frost blink, because i can not burst in the same spot.
When i hold down my rightclick, i keep going forward. meaning at a boss i have 10 precise changes of mouselocation per second, 1 little fuckup and im 3 screens away from the boss.
Here on youtube some dude seems to have a setup to cast in place... how do i do this?

https://youtu.be/B9b3p-qjqKc?t=144