Sand the entire surface of the cinder block wall using a sanding buffer with a medium-grain sanding ring. This will smooth down any rough or uneven areas that might interfere with laying the porcelain tiles.
Vacuum the wall and surrounding areas using a shop vacuum with a brush attachment. This will remove small particulates of concrete and dust from the cinder block wall.
Spread a 1-inch-thick layer of medium grout over the surface of the cinder block wall, using a trowel. Apply the grout in an even layer.
Press porcelain tiles halfway into the grout on the wall, spacing each tile 1/4 inch apart. Use tiles as large or small as you prefer.
Spread a 1/4-inch thick layer of medium grout on the top of the tiles with a trowel. Scrape the excess grout off the tiles with the same trowel.
Wipe the surface of the tiles clean using a washcloth. Run your finger along the creases between the tiles to create an even layer of grout. Allow the wall to dry for 12 hours.
Fill a paint tray with clear sealant. Apply the sealant to the entire wall using a paint roller. Allow the sealant to dry for 8 hours.