self-rising flour vs premix

self-rising flour and premix both are nouns.

Word	Noun	Adjective	Verb	Adverb
self-rising flour	Yes	No	No	No
premix	Yes	No	No	No

As nouns, premix is a hypernym of self-rising flour; that is, premix is a word with a broader meaning than self-rising flour:

self-rising flour: a commercially prepared mixture of flour and salt and a leavening agent
premix: a commercially prepared mixture of dry ingredients

Other hypernyms of self-rising flour include mix.

self-rising flour (noun)	premix (noun)
a commercially prepared mixture of flour and salt and a leavening agent	a commercially prepared mixture of dry ingredients