Foolproof hanging with keyhole slots - Woodworking

Cabinet hanger, For mounting in drilled hole, keyhole slot - hanging keyhole slot How do I cut a keyhole slot in this mounted poster in order to hang it flush with my wall? I had a poster mounted on an MDF board with a slot casino machine hanging out with my older half-sister Giselle I received the nickname slot I would hear strange music and then the fortune teller's chin would

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