instance vs flesh out

instance is a noun but flesh out is not a noun.

Word	Noun	Adjective	Verb	Adverb
instance	Yes	No	Yes	No
flesh out	No	No	Yes	No

As verbs, flesh out is a hypernym of instance; that is, flesh out is a word with a broader meaning than instance:

instance: clarify by giving an example of
flesh out: add details, as to an account or idea; clarify the meaning of and discourse in a learned way, usually in writing

Other hypernyms of instance include dilate, elaborate, enlarge, expand, expatiate, exposit, expound, lucubrate.

instance (noun)	flesh out (noun)
an item of information that is typical of a class or group
an occurrence of something

instance (verb)	flesh out (verb)
clarify by giving an example of	become round, plump, or shapely
	add details, as to an account or idea; clarify the meaning of and discourse in a learned way, usually in writing
	make fat or plump