Rock wizard create an impossible-looking stone cairn

In this impressive video, a dude in a stream shows his wild rock balancing skills. I've only ever seen vertical rock towers, but this skilled guy arranges the stack of rocks horizontally like a bridge, wedged between two boulders. The only thing keeping them in place is the way that they are tightly  sandwiched together.

It takes the guy multiple attempts to get this right, and after he does, he adds a vertical rock tower on top of the horizontal one. To top it off, he adds a rock to the top of the vertical tower that is much larger than the ones underneath it, and it seems nearly impossible that he was able to get all of this to balance.

I wonder how long it took him to get to this pro level of rock balancing. I'd feel like a wizard if I had this guy's skill level. Watching this video in a timelapse was very cool, but I'd love to know how long the entire process took him.

See also: 

The Kummakivi Balancing Rock is one strange rock