Print a reverse copy of the image you plan to transfer using a laser printer, or photocopy a non-toner-based image using a toner-based copier
Cut out the image, leaving enough margin to handle the paper without smudging the image.
Lay the image, toner side up, on your work surface.
Brush a thin coat of gel medium over the image using a foam paintbrush, taking care to cover it completely.
Apply the image to the tile, gel side down. Smooth the image gently with your fingers to adhere it completely while removing creases and air bubbles.
Scrape the paper back and forth gently with the edge of a credit card to burnish the image off the paper and onto the tile. Hold the paper firmly to keep it from slipping as you burnish.
Let the tile sit for at least four hours, or until the gel medium is completely dry.
Wet the paper with water. Wait several minutes for the water to begin soaking through the paper.
Rub the paper off the tile with your finger. It will rub away in small bits. Work gently. Re-wet the paper, if necessary. Take care to avoid damaging the image.
Allow the image to dry completely after all the paper has been removed. Spray or brush on a coat of non-acrylic sealer to protect the image.