One of the unique aspects of a glass wall plate is that unlike your typical switch cover, it's flat in the back, Installing a glass switch plate really should be no different than putting up any other. In a perfect world all electrical boxes are positioned properly. However, If your electrical box is too close or too far from the wall opening you may have to adjust the receptacle screws. Tightening the screws will pull the switch plate closer to the wall.
To assure that the plate will fit snuggly against the wall you can use an acrylic spacer or gasket to fill the gap. These peel and stick-on gaskets are easy to apply and available in single, double, triple and quad templates. They can be purchased with all our glass plates. See Switch Plate Gasket.