You order your cabinets to have a top face frame rail (vertical is a style horizontal is a rail) to match the reveal of your cabinet door spacing, if they are frameless you may need to add a filler to the carcass top and nail the crown into that.
Hopefully if they are a euro frameless you'll have that space, most don't, as they are overlay doors.
Crown on cabs typically are pinned together with 18 ga. and only nailed to the cabs at the bottom, the tops of the cm is glued and may be pre-assembled if they don't meet with the ceiling.
Cabinets are square and true- for the most part- ;)- so the compounds work. You can rip stock to the spring angle but it's really not needed in most "cases", (no pun intended).
Every job is different though, so...
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