The idiom 瑕不掩瑜 is formed through a straightforward syntactic arrangement where 瑕 (flaw) acts as the subject, 不 (not) negates the verb 掩 (to cover), and 瑜 (jade's luster) serves as the object, resulting in a literal clause meaning "a flaw does not cover the jade's luster", which inherently expresses the idea that a minor defect cannot overshadow main virtues.