Start by placing the 1/8″ thick 32″ long pieces around the base of the newel post. Prior to clamping, add Liquid Nails to the edges and added supports on the inside with wood scraps and paint sticks.
Now it is time to build up the base of your squared newel post. Do this by adding the 3/4″ thick 18″ long mdf around the very bottom, and follow the same steps of wood glue, clamps, and nails.
To cover the “ball” on the end of the post, put together a smaller box of the 1/8″ thick mdf. Use wood glue, clamps, and small 3/4″ finish brad nails to hold the box together until the glue is dry.