Start by assembling the outer rectangular cabinet shell measuring thirty-six inches wide, sixteen inches deep, and eighteen inches high from three-quarter-inch hardwood plywood. Cut a continuous forty-five-degree bevel along a four-inch-wide hardwood board to create a heavy-duty French cleat mounting system, fastening one half securely to the upper interior rear rail of the cabinet. Use a jigsaw to cut an eight-inch cat portal through the bottom base panel or lower side panel, attaching a small, wrapped sisal rope climbing step directly beneath the opening on the wall. Mount the coordinating wall cleat directly into at least two structural wall framing studs using three-inch heavy lag screws, checking for level with a four-foot spirit level. Hang the credenza onto the wall cleat, locking it with safety set-screws driven through the lower interior back rail. Install painted front cabinet doors on soft-close European hinges to complete the floating installation.
