[noun] + のうち(で) + [noun] + が一番 + [i-adj] [noun] + のうち(で) + [question word] + が一番 + [i-adj] [noun] + のうち + [number] + が
のうち follows a noun and means "of", "out of": it names the set you are picking from. で after it is optional, and with a superlative you often see のうちで.
With a number after it, のうち gives a part of the whole: "three out of ten". The part usually takes が.
In a superlative, のうちで and のなか中で mean the same, and のうち sounds a little more formal. のうち needs a set of separate members – people, books, seasons, questions. For "inside a place", only の中で works.