First, take some foam board and cut it to the size of the floor piece you want. Then glue together Hirst Art bricks in the outer edge design that you want. Place the outer edge on the foam board and trace out the inside of the foam board. Then, (and I didn’t do this part so bear with me) hollow out the foam board until you have all of the foam out and just the other out layer. It’s just fine if the foam board isn’t made completely smooth from hollowing it out. That adds to the texture.
Then take some larger sand. I bought this kind from Hobby Lobby. I am not sure of the name of the brand but it’s just the larger granular sand. Put as much as you need, and you really don’t need a whole lot, into a snack baggie. Drop a few drops of black acrylic paint into the baggie with the rock sand. Then it’s like using Shake ‘N Bake. I also just kind of massaged all the sand until it was all coated. Since the rocks are going to be wet I dumped them out onto aluminum foil (parchment paper would work) and then let it all dry. This doesn’t take long at all. If it clumps at all you can roll it around in your fingers to break it apart.
Now I wish I had more pictures of my steps but I didn’t realize it would be so well received! Your next step is to paint the foam board. In the first image you can see that I have painted the top edges black. Since you don’t perfectly cut the foam board around the bricks, as these have rounded edges, you will still see the foam board. Painted the edges black helps hide them and makes it barely noticeable. Now, starting from the inside of the foam board back sure that up the walls of the foam board you paint it black. Also, on the bottom of the foam board paint an outer circle of black. Then, in the middle paint it the brightest orange you have. I used Apple Barrel’s Pumpkin Orange but any bright orange will work. Next, I dab small amounts of yellow and on between the orange and black on the floor I paint a bit of red to fade the black into the orange.
Once that has dried, which your rocks will have dried too by then, sprinkle them on top. Don’t put too many on there as you want the color to peek through but as much as you would like will do. After you have them how you want them arranged, spray the whole inside of the foam board with a type of thin spray glue. I used Scenearama’s Scenic Spray Glue, that’s typically used on sprinkle scenery grass. Spray generously. You are trying to seal and lock the “coals” into place.
Now wait for that to completely dry. Don’t get impatient like I tend to our on this next step you will push the coals around. After it’s dry, dry brush, very lightly, an ash gray. I looked up many pictures of coals to try and get this right. If you want some that look like they have been burning longer dry brush more ash gray. If you want them to appear hotter just use a medium amount. That is what I used.
Mitch Michaelson, from Terrainosaur.com, created a video tutorial of this technique. Thankfully, he is incredibly talented and has the equipment to make these! Check it out!