Happy stones are painted stones that people make to leave behind in nature for the lucky finder who takes them or puts them down in another place.
It's actually very simple you need stones and water-resistant paint and a protective varnish so that your artwork does not fall off.
Don't hide them
A tip for better results, first make a sketch with a pencil and color it in. When you're done, don't forget to apply Protection.
When you're done you can spread them out in the walking areas but don't hide them because people who don't go looking for the stones should be able to find it that way too.