Using 2x4s and a drill, attach four boards to the top of the vanity (two in the back, two in the front) to create the base/frame of the countertop (Image 1). Attach the last 2x4 to the front of the other boards to create a lip for the countertop (Image 2).
When the countertop is formed, cut a hole(or holes) where you want the sink(s) to be.
Spread thinset with a trowel on one half of the countertop (Image 1) and set sheets of travertine tile over the area (Image 2).
Tile the countertop in sections so that the thinset won’t dry while you're laying out the mosaic glass pieces.
Once all mosaic pieces are set in that section, lay more thinset on the other half of the countertop and continue the process.
Once all tiles are set, let dry, then grout over the entire top and sides of countertop. Wipe countertops clean with a wet sponge.