Locate the area along the interior section of the trayed area where you want to mount the shelf. Hold the back plate for the floating shelf against the area and make pencil marks where the screw holes are located.
Create a pilot hole using a drill at each location of the pencil mark. Install wall anchors by screwing them into place if there are no studs behind the tray section. Screw the back plate into the wall anchors or directly in place.
Line up the floating shelf with the back plate and slide it into place.
Fill the floating shelf with decorative items that have enough room to clear the ceiling.