Rip oak plywood into four pieces of the desired column width and height. You don't have to rip them at an angle, since the trim will cover the cut edges. Attach three of the pieces with glue and nails to make a long, three-sided box.
Cut two pieces of scrap 1" x 1" (or other scrap wood) to a length that's about 2/3 of the width of the box. Glue and nail those pieces inside of the box to the top of opposite sides.
Use the stud finder to locate the joist to which the pole is attached. Place the box around the post so that the pieces of scrap wood are under the joist. Fasten the box to the ceiling by nailing through those pieces from below into the joist.
Glue and nail the fourth piece of oak plywood to complete the box column.
If outside-corner molding is being used for the trim, glue it to the corners of the column. Use the finish nailer to secure the molding. If another kind of molding is preferred, cut it lengthwise on one edge to a 45-degree angle. Glue and nail the molding to the column, fitting the angled edges together at the corners. Add any additional trim with glue and nails.
Cut the crown molding to length; the bottom of the molding should be the same measurement as the column width. Miter the ends at 45 degrees. Keep in mind that the crown molding must be flipped over when it is being mitered (pretend the base of the saw represents the ceiling). Glue and nail the crown molding to the top of the box column.
Cut the base molding; the top of the molding should be the same width as the column. Miiter the ends of the molding at 45 degrees. Glue and nail the base molding to the bottom of the box column.
Fill the nail holes with wood putty. Sand and stain the column.