Determine miter saw angles for crown molding by deciding if you can cut the molding vertically or must use the flat method. Other factors influencing angles include the type of corner and the side of the corner you are cutting. The flat method requires compound miters and referring to a miter- and bevel-angle chart if the corner is not exactly 90 degrees.
For a vertical cut, place the decorative side of the molding against the fence and the top of the molding against the table. Set the saw for a 45-degree right cut for the right side of an inside corner, and save the right cut. Set it for 45-degree left cut for the left side of the inside corner, and save the left cut. Use a similar approach for the outside corner, but save the opposite cuts.
For 90-degree corners using the flat method, place the broad flat side of the molding on the table and the top against the fence. If the saw allows beveling in both directions, there is no need to flip the stock. The bevel angle is 33.85 degrees and the miter angle is 31.62 degrees. For left-side inside corners bevel left and miter right, saving the left end or the cut. Right-side inside corners require a right bevel and left miter, saving the right end of the cut. Reverse the bevel and miter angles for the outside corner.