Wiktionary
unpretentiously
adv. In a manner that is not pretentious; sincerely, without affectation.
WordNet
unpretentiously
adv. in an unpretentious manner; "she was unpretentiously dressed even though she was the guest of honor" [ant: pretentiously]
Usage examples of "unpretentiously".
Leaving aside the fact that Berry's chair was neither elevated nor any larger or fancier than any other, she was comporting herself far too casually and unpretentiously.