We have kraftmaid cabinets and a sinkology fireclay sink... it's a 30" sink in a 33" cabinet. Not sure what you mean by plastic box... I am not a pro but our installer (friend with 20 yrs experience) had no issues doing this. We added a DIY drip ledge in the front also. Some pics, hope this helps.
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no bevel below cabinetry - nice after
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