What You Need
Two 22-inch-square pieces 3/4-inch medium-density fiberboard (MDF)
Router with straight bit
Two 14×22-inch pieces 3/4-inch MDF
Screwdriver and screws
Draw an X on each of the two 22-inch-square MDF pieces to find the center. To create the round top and bottom, pin the end of an 11-inch-long string to the center of the board and attach the other end of the string to a pencil. Trace a circle. Use a straight bit on your router to cut out two circles. Sand the edges.
With a jigsaw, cut a 3/4-inch-wide notch halfway through the center of each of the two 14×22-inch MDF pieces along one long edge. Slide the two pieces together.
Apply wood glue to the joined rectangle and let dry. Center the assembly and glue on top of one of the round pieces. Apply wood glue again and place the second round piece on top of the assembly.
Hammer several finishing nails through each round piece to secure them to the upright pieces.
Add a small amount of wood filler in each of the nail holes (e). Smooth wood filler with putty knife.
Prime and paint the ottoman; let dry. Use a screwdriver to attach casters to the bottom of the ottoman below the cross pieces; set in far enough so the entire wheel is under the ottoman when it swivels (instead of sticking out the sides).