I have a little tool that measures the angles for me.

http://www.menards.com/main/tools-hardwa...6019-c-9149.htm

That helps with finding out the primary angle, but then you need to use your miter saw to cut that angle while holding the crown molding upside down and at an angle that holds the inside top and bottom edges flush with the base of the saw and the fence...

YouTube videos are helpful. If they start talking about 30-something % angles, it gets confusing, find a different video.

Farewell - June 4, 2020