I'm installing crown molding for the first time. I have a square room that is a 12 x 12. I know that I need make all inside cuts on the crown molding. I have seven 8ft crown molding lengths. How do I measure the crown? Do I measure from the top angle of the crown that sits against the ceiling. I want to make sure I measure correctly so I get a good tight fit in each corner with the inside cuts. Thanks for any help. Regards.