Jeffrey Bale is the creator of most of these mosaic stone paths. He has posted general directions on his website. Several people have also posted links to instructions. You can also google instructions. These are not as easy to create as they look…lol, and I don’t think you’ll find specific instructions to recreate one of his installations. He mainly gives directions about sorting rocks, adhesives, planning, and measuring.

I learned to do the design in reverse sticking it to tracing paper with flour and water paste then turning it over onto wet cement and level it off. Once the cement is dry wet the tracing paper and peel off. This helps keep it all level. Another way is pressing stones into a frame/wooden tray of 1 inch sand then back fill with cement turn over when dry.

I think the thing they are spraying is water and they have lain the stones into dry cement. You just water it and let it set. then fill with grout and polish it all up. You can varnish the stones as well so they always look wet and shiny.

ehow.com/how_8749004_build-river-stone-path.html

Here are two places with instructions, fabulous finds.
jeffreygardens.blogspot.ca/2011/08/building-pebble-mosaic-stepping-stone.html
and
thegardenglove.com/diy-garden-stepping-stones/