Supports are mounted to the wall framing before the walls are finished out...that way they are hidden.

Hi, great question. This vanity is attached to the wall on either side and has a steel support structure below to ensure that is securely attached to the walls. We positioned the vanity 3 inches forward of the floor-to-ceilling mirror to create a dramatic illusion of depth. Our stone fabricator was able to cut the slabs of white marble to the exact size for a perfect fit. We used sink by WetStyle and special short p-trap to eliminate any chance of seeing unsightly plumbing below or in the mirror! All the details count! Thanks for asking and good luck with your projects. - dSPACE Studio

You can do a simple vanity with two 2 x 12 and either legs (jacks in the wall ) formed as a box and nailed or best screwed to the wall. Remember to add led down lights. You can also cut the duplex out let in the front if you center your hole.