JordanTheBigBoy is right, you want to get enviroment kills then jump on the nearest wall asap.
However, I found it easier to do this on Watchpoint: Gibraltar, than Lijiang tower. You're more likely to die on King of the hill maps in my experience.
On Gibraltar you can do it at the cliffside near the beginning, or at the end.
Here's a video of how I got it.