It's hard to tell just by looking at this photo, but the shelf pictured here used to be part of a cabinet. Someone added a plank for a shelf and some hooks to hang from. You could also use a panel from a door, but the principle is the same. All you need is a drill and some screws and hooks. Oh, and you might need a saw to cut the panel away from the original piece of furniture.
After assembling everything, you can use a stencil to paint this message or a different one depending on what you want. However, we can really relate to the message pictured here.