Measure the length of your wall. Select a section of crown molding that's longer than this distance.
Set the miter saw box to cut a 45-degree angle.
Turn your crown molding so the front is facing away from you. This position gives you the proper angled cut for an inside corner. Cut the molding to fit and return to the wall.
Place crown molding in the corner and use a nail setter to set the nail below the surface.
Fill in any gaps, seams or nail holes with a wood filler and paint.