If you click through to the actual blogpost, cinderblockplanter , you’ll notice that it takes you a blog, Traditionally Modern Design. Reading the actual description, the original creator used cut up cinder blocks and liquid nails. You can also use heave duty canvas, mesh, or concrete board and liquid nails to get the same effect. I’d probably use the canvas or metal mesh so that moisture would not collect, but note that the canvas will have to be replaced as it can deteriorate over time.

-v.