The look of it reminds me of coquina stone which makes it a natural for the Florida garden. And, this particular trough has been decorated with seashells...a favorite of mine...pressed onto the rim of the container.
Below is a sideview.
She did a wonderful job selecting the succulents which look great in this type of container. So, am I going to try and make some more? You bet! And, you can to with these instructions I found from Fine Living. I guarantee you'll love the results and your new unique faux stone containers.