The silicone this was made of reminded me of the great Hirst Arts molds so I just used it the same way. First I mixed up a slightly thick paste of Durham's Water Putty plaster and filled the hex shapes. I tapped the cardboard that the trivet was on to remove air bubbles, this took a while, and then smoothed it a bit. I wanted each hex shape to cast separately so once the putty had thickened a bit more I scraped it perfectly flat with a plastic scraper.
Once the plaster has set I put it in a 200 degree oven until it was perfectly cured and dry. At first I thought I'd demold them into and then lay out the hex pattern but I had a better idea. I left them in the mold and then put thick super glue onto the top of each hex. This way all I had to do was press a base down on top, let the glue dry, and then demold the pieces. This would leave me with perfectly spaced tiles without getting too fiddly. I was a bit too eager so some of the hexes popped off in the mold or fell off the base. I glued some of them back on but mostly left them as they were. My intention was to make a base that represented a temple or building that had been destroyed by time and weather so if they were broken or misplaced it would just add to this effect.
Once the super glue set I mixed up some plaster to act as grout for the tiles. After glopping a good amount over the tiles I used a wet finger to smooth the grout and remove any excess. I also used the plaster to build up some ground around the tiles. I wanted the bases to look like the building that had these tiles had been overrun by nature and now only the dirty tiles remained.
Once all of the plaster was dry I added some sand glued in place with wood glue. Painting used drybrushing and Citadel washes to really dirty them up. Static grass adds some life to the feeling of encroaching nature. Although you can get a similar tile effect using textured plasticard I think this gives a bit more realism by having individual tiles to crack or chip, or to remove altogether. And the bases come together pretty quickly and very cheaply. The trivet to use as a mold was $4.95 and the plaster cost pennies for the amount that I used.
I think this effect could really work well for a jungle themed army like lizardmen, elves or space elves, or maybe a middle eastern theme. Give it a try and let me know what you think.