Turn off the electricity to the backsplash wall and remove the outlet covers from the backsplash with a screwdriver.
Layout the glass tiles on the countertop in front of the backsplash to determine how many tiles will fit in the area and where cuts will need to be made. Pay attention to the area where the outlets are.
Use a razor blade to trim any mosaic glass tiles to the approximate size needed to fit around the outlets and fit the edges of the installation.
Spread white, latex-modified thinset mortar onto the backsplash area and smooth out the trowel marks. Install the glass mosaics up to the areas where they will be fitted around the outlets.
Use wheeled glass tile nippers to cut the individual glass mosaics to the correct size to fill in the areas around the outlets. Spread a small amount of mortar onto the backs of the individual tiles and press them into place around the outlets.
Let the tiles dry for 48 hours and grout the backsplash with an epoxy grout float. Stop grouting just before the tiles that come directly in contact with the outlet boxes and around the edges of the installation. Fill in these areas with caulk.
Wait 24 hours and reinstall the outlet covers.
Spread white latex-modified thinset onto the backsplash area and smooth out the trowel marks. Press the individual tiles into the thinset and twist slightly into place.
Hold the glass tiles that will be installed around the outlet directly in front of the box. Trace the outline of the outlet box onto the backside of the glass tiles using a grease pencil.
Make two intersecting cuts on the tile using a tile wet saw with a glass cutting blade. Cut the tile backside up to minimize chipping the front of the tile. Push the glass through the blade slowly until the first cut meets the intersecting line. Pull the tile back, turn it and make the second cut until it intersects with the first, removing a notch that the outlet box will fit into.
Spread mortar directly onto the backs of the cut tiles and press them into place around the outlet covers.
Wait 48 hours for the mortar to dry and grout the glass tiles with an epoxy grout float. Use caulk to fill in the areas around the outlets and the corners, or 90 degree angles, of the installation. Wait 24 hours and reinstall the outlet covers.