When cutting the small return cap of the architrave bead, I slide the fences on my Kapex saw in as close to the blade as possible.
I cut the first self-return cap for the crown. Next, I swing the saw, and cut an outside-corner miter.
At the opposite end of the molding, mark the measurement on the same part of the profile, where the miter will pass through the bottom fillet.
For gluing the small self-returns to the frieze, architrave, and crown, 2p10 cyanoacrylate glue works well.
Yellow glue provides some wiggle room for aligniing the miters on the crown molding. Hold them in place with spring-loaded miter clamps while securing the molding with 1-inch 23-gauge pins.
After applying a thin line of glue to the top of the frieze, clamp the crown to the frieze, making sure the crown is flush with the back of the frieze and proud an equal amount at each end.