Measure for the crown molding, using a tape measure. Note the angles for surrounding the fireplace. Most crown molding pieces added around a fireplace will require 45-degree angle cuts.
Transfer the measurements to your crown molding pieces, using a pencil.
Set up a power miter saw for cutting the crown molding.
Line up the marks on the crown molding with the cut line for the saw for straight cuts. Hold the molding with one hand, start the saw and pull down on the handle to cut the molding.
Adjust the table to the 45-degee mark for making an angled cut. Place the molding on the table, hold the molding with one hand, start the saw and pull down on the handle to cut the molding.
Sand the cuts lightly to remove any burrs.