Use your belt sander to dull the surface of the counter, getting it free of shine. Wipe up the dust.
Measure across the length of the countertop at the front edge, and mark the middle with a pencil. Use the pencil and square to mark a line from front to back, dividing the counter in half.
Spread tile mortar over the front edge of the counter with a notched trowel.
Press the first trim tile into place in the mortar on either side of the middle line, working from the line to the sides. Put spacers between the trim tiles as you hang them. Cut the tiles at the two ends to fit, as needed.
Set the first course of standard porcelain tiles behind the front row of trim tiles, again starting at the center line and working to the sides. Set spacers between all of them. Cut the tiles at the ends as necessary.
Set the second course in place behind the first, again starting at the center. Repeat the process, working your way back over the surface course by course, putting spacers between all the tiles and cutting the end tiles as needed.
Let the mortar set for 12 hours. Pull out the spacers.
Grout the tiles with a grout float, pressing it into the spaces between the tiles. Wipe off the excess grout with a damp sponge.