Thinking of doing something like this in the "path" we always walk on across the lawn. It's getting worn down and I can't get everyone(including myself sometimes) to go around on the sidewalk. Step-by-step: Flagstone path
How to Install Stone or Brick Over an Existing Concrete Pad
How to Lay Flagstones on Dirt - and yes, you can if you have soil with minimal organic matter and no erosion or drainage differentials in the area you set the stone. I'll probably fit small stones in between the cracks to hold the crack widths.