Lay the wood trim pieces out flat on a tarp. Paint or stain the trim in a color to coordinate with the tile on the counter, using a paintbrush. Let the trim dry completely.
Measure the front edge of the counter with a tape measure. Mark the back of the wood where it should be cut to match this measurement, using a pencil.
Place the trim in a miter box so that the marking on the back of the trim is lined up with the 45-degree angle on the box. Look closely to ensure that you are cutting the angle in the right direction for installation.
Start with the miter saw at the back of the miter box and saw from back to front.
Spread construction adhesive along the back of the trim piece. Press the wood into place. Hold the trim to the counter with one hand while you insert finish nails through the wood and into the counter with a nail gun. Place a nail every 4 to 6 inches.
Repeat this process for the sides of the counter, matching the edges so the pieces will fit together neatly. Use the miter box to guide your saw.
Fill all of the nail holes with wood putty. Spread the putty into the hole with your fingers. Spread wood putty onto the corners where the wood trim meets to fill any small gaps. Let the wood putty dry completely.