It's so easy....and ridiculously inexpensive!
What you need: Gloss gel medium (I used a Liquitex medium..but I think Golden also has one), laser prints, scissors, a ruler, & kitchen tiles.
*It is important to realize that these images will be reversed (not inversed...but reversed) when you take them up* (just thinking if you are using verses or a text on your coaster - you'll have to switch it around in Photoshop).
First decide what images you want to use. You may need to resize them in Photoshop (I know I definitely did). Put them on one sheet to save the cost. Send them somewhere that prints on laser printers. I just sent mine to Staples. It cost like 39 cents or something.
Cut out your images and make sure they fit on the tile properly. If not, do a bit of a trim up.
Use your finger or a brush to cover the tile in your Gloss Gel Medium. Make sure it's a nice thick coat. Then place your image on the tile as you wish (image side down). Place it firmly and make sure there are no bubbles or bumps.
Let the tile(s) sit for 6-8 hours.
Now it's time for the mess! You'll need to be near a faucet or have a pan of water handy, as well as a rag. You may even want rubber gloves. Your fingers will feel pretty raw afterwards if you use your bare fingers (like I did....). Soak your rag and place it on the tile for a minute or so. Let your tile absorb the water. Now, remove the rag and slowly start rubbing where the image is. You'll notice that the paper will start to come up. Continue to scrape/rub the paper off. You'll start to notice your image on the tile! You'll get to the point where it looks like your coaster is done and ready to go. However, you'll probably notice as it dries that there is still paper covering the image. You may have to do this several times to remove all the paper. But once it's done, it looks beautiful!!!! And, you can even do this on wood and other surfaces! Now all I have to do is add some felt to the bottom and coat in varnish (for extra protection)!