Thanks everyone.
No I don't put anything in them. I found it got to be too difficult to try and cover up or I had to make them thicker than I wanted which made them too heavy. Most people won't step on them anyway if they are decorated. I found they thought they would ruin the paint job or the stones. I use them all the time and have not had any break. (knock on wood) The resin ones from the store breaks real easy the concrete is not as easy. if you make it to thin then they might break. I like the to be at least an inch thick.
