I make frameless cabinets and want to improve my method of attaching crown moulding. I am interested in ease of installation as well as final appearance.
We attach our crown moulding to a 3 inch strip of the same species veneer particle board with headless nails and glue, cut to size and pre-assembled in-shop with a small overhang to allow for out-of-square walls. It works well for us. We screw the finished piece to the cabinet from on top or inside, depending if there is space between the ceiling and the cabinet. These are kitchen cabinets in wood or laminate and we stain the crowns and light valance to match the laminate.
We have just tried attaching a strip of 1/8 masonite to the top of the 3 inch particle board and cut a matching groove in our crown moulding, so that the bottom of the moulding automatically lines up with the bottom of the strip. This is useful for long mouldings.
Most of our cabinets go to the ceiling, or to a soffit, so the extra strip at the top gives us a bit of room to hide out-of-level ceilings. One drawback is we have to make and field-install a stop block for pairs of doors, as there is no top to land the doors on.