Here on a video videos that show the handstand on slackline stunt. This is not an easy one to do. I would highly recommend you learn how to stand on your hands on solid ground first and also how to easily stand on a slackline on your feet too, before you try to put the two together.
I like the excitement here at muscle beach in Santa Monica as several people perform these handstands.
Here is another way to do a handstand on the slackline from already standing on top of it.
I’ve seen some professionals even do one handed handstand on the slackline, so this stunt can be taken pretty far.