Frame it onto a backing of plywood. Materials: Plywood backing, strong (thick) enough to carry entire weight Mirror clips, probably the strong, flat metal type (example). Decorative clips typically will not support a large load. Decorative molding to hide the clips and dress up the framing. Possibly flat molding, about the thickness of the mirror, to rest the decorative molding on. Steps: Decide on what decorative molding you want to use (if any). Cut the plywood to the mirror's size + molding size. (add frame attachments, see below) Cut the molding to size to run around the frame. Paint or finish molding, if desired. Note: you can buy pre-finished molding to save time. Center the mirror and attach securely with clips. Most clips have weight suggestions so you can safely determine how many you'll need. You can also use epoxy / glue (example) to glue the mirror to the plywood, but this may warp the mirror and/or hurt the mirror-finish. Attach the molding around the mirror, hiding the clips by slightly overlapping the mirror's edges. If the molding is lifted up too much by the mirror's thickness, add flat molding underneath to bring the decorative molding flush with the mirror's surface. Done. If you want to hang to mirror, at step 3 secure these attachments to the plywood backing. It will be easier to do this before mounting the mirror. Finally- 8. Post your Instructable on mounting a big mirror!