Drink holder stone porch

Are those stones made with egg cartons? Is there a place where I can find some step by step instructions? I know there is somewhere, but I haven't had luck finding it. Thanks.

I used those to-go drink carriers, I didn't use a tutorial, just cut the "stones" out into the shapes I wanted gluing them with the textured side up and once they were all in place grouted them with some Dap fast and final mixed with a little grey paint. Then I did a dirty wash and then painted them individually with different shades of greys and browns.

Please let me know if you need more help, I only had time for a short reply but can help you later on this evening if you need