I came upon this idea after reading about paver forms in the Home Depot Outdoor Projects 1-2-3 book. If you can make square pavers why not go the extra distance and make a form based on the work of M.C. Escher? Rather like the early 80's Shmuzzle Puzzle.
Someone had already beat me to it: www.geckostone.com. These forms look great and the pavers look very nice, but I wanted something a little more angular and without the lizard effect. I was more interested in the interlocking shape rather than the fact that it is the shape of a lizard.
completed form, ready for concrete
So I decided to attempt my own form. The area of the paver is described by a hexagon. I drew the "shmuzzle" as well as the basic hexagon in Adobe Illustrator, printed it and laminated it to a square piece of Sintra. I realized that the Sintra would not be sturdy enough for the concrete so I attached the Sintra to a metal plate (actually an old "Do Not Enter" sign).
I decided on 3" tall sides - made from short cuts of wood. The wood was fastened through the Sintra and metal plate with wood screws (about 2 screws per length of wood). I knew it wouldn't line up perfectly, but I figured since the shmuzzle was about 1/8" smaller that the pavers would fit together with a bit of space between them.
To the right, you will find the original file that I created in Adobe Illustrator to use as the base for the mold. You can click on it to save it for your own use if you wish.
If you notice, the actual area of the paver is found by computing the area of the hexagon described in gray.
The first time I attempted to create the paver, I used regular Quikrete with no release on the edges. While the mold dried quickly and solidly, it was impossible to remove the paver without breaking it, as seen in the picture.
For the next attempt, I used plastic wrap to seal between the concrete and the form. Unfortunately, I was unable to force the plastic into all the nooks and crannies and the resulting paver, while more solid, was much more mis-shapen.