Print out the photos on a dry inkjet or laserjet printer. Make sure they are sized to fit the block.
Working one image at the time, use the sponge brush to apply photo transfer medium to the front of the photo - obscuring it completely.
Smooth the image down carefully onto the block. Wipe away any excess that comes out the side. Repeat with the remaining five sides and let this dry for at least 24 hours.
When the 24 hours have passed, wet the block on one side. Rub lightly to remove the paper. Let the image dry and repeat on the remaining sides.
After removing the top layer of paper, let dry a little and then repeat. It's better to rub gently and repeat the wetting process several times than to rub too hard and rub the image away.
The finished block will end up looking slightly faded and vintage-y - this is normal. Add a layer of Mod Podge Hard Coat to darken the photos and seal the block. Let dry completely before displaying.