I hope this helps. I used to make lots with scrapbook paper/paper designs that I made/paint chips to sell. You would want to hot glue cork onto the bottom of the coasters to keep them from scratching anything & also to keep any cold/hot from affecting the table. As for sealing, first you put mod podge on the tile itself and put the paper on top of that to glue it to the tile. After that, brush a coat of mod podge across the top of the paper in one direction. Once that dries completely, brush another coat going sideways from the first one. That will seal the paper from getting wet. I always like to take it a step further and spray a coat of clear sealant (you can buy it on the spray paint aisle) just to be safe. This keeps the mod podge from sticking to anything. I live in Alabama where it’s really humid, so dust sometimes sticks to the mod podge if I don’t use that extra sealant layer. If you go to instructables.com you can find instructions with pictures for basically anything you could ever want to know how to do, crafty or otherwise.