Position the column on top of the slab where you intend to attach it. Trace around the base of the column to mark the location. Post base brackets are available in several sizes for round and square columns; select one that fits your column. Align the bracket with the post base outline. Mark the screw holes around the perimeter of the bracket.
Drill a pilot hole in each marked location with a 3/16-inch rotary mason's bit. Do not use a hammer bit unless you are using a hammer drill. Wrap a piece of tape around the bit, 2 inches from the tip. Drill each hole to a depth that places the tape even with the top of the bracket. Blow the dust from the hole.
Drive one 1 3/4-inch Tapcon-style concrete screw into each hole in the bracket. Drive the screws in until the head is firmly pressed into the bracket. Use the screw tip that comes with your concrete screws, or purchase the label-recommended square point Phillips-head bit for best results.
Stand the column in the bracket. Drive 1 5/8-inch treated deck screws into the column through the holes in the flange of the bracket.
Install base trim on all sides of the column, covering the bracket. Round columns typically come with a trim ring. For square columns, cut four pieces of baseboard molding with 45-degree miters on each end to frame the base of the column. Nail the trim in place with finish nails every 6 inches.
Caulk the seam between the trim and the slab with 100 percent silicone caulk. Caulk nail holes and small gaps at corners and the top of the trim with painter's caulk for painted columns or wood filler for stained columns.