Nowadays, it is hard to add the kitchen cabinet crown molding since there is no materials on the top of the doors where the crown molding can be fixed. You can add a hardwood frame which sits at the top of the cabinets and you can use it to be a base for fastening of a crown. In case the ceiling is not leveled up, you have two different options. You can leave such gaps or you may scribe-fit the filler strip which makes a round contour at the ceiling.
You should start by removing the existing molding with a hammer and a flat pry bar. You can then hold two different short flat against the ceiling or the overlapping of the cabinet corner. Make a line where the overlapping boards can meet at the outside of the corner. Use the combination of the square to draw the lines on the board that connects the corners on both the outside and the inside. You can stack the miter saw table and to adjust the blade angle so that you can make the pencil line.
Measure the length found within cabinets starting from one corner to the other to know how much crown molding you need. You can set the saw blade miter angle and use a guide block. Cut the miter joints and cut the crown molding you need. Hold the crown molding at the cabinets and tie it to the ceiling and nail it at the cabinet by the use of a pneumatic brad nailer. Cut mating angle at the next piece of a crown you want to make and apply using the carpejter glue on the end of the molding. You should hold the second piece of a crown too tight against the first piece and to nail it at the cabinets. You should repeat the same process for all the crown molding you want to add.