Take an object. Design it, make it look three dimensional. Then start putting elements on top of it, all of them contained within the borders of the icon-square. Now you’ve made a Dimensional Surface Icon.
How is this different from the Picture Frame Icon? Because all of the elements are contained within the icon itself. The bounding box for the icon mark the edge of the object the elements rest upon.Picture Frame Icons will feature elements that expand beyond the limits of the square.