The correct spelling of the phrase "seeing one uncle" is /ˈsiːɪŋ wʌn ˈʌŋkəl/. The first word, "seeing," is spelled with two "e's" because it comes from the verb "see," which has a double "e" in its base form. The second word, "one," is spelled with an "o" and an "e," as it represents the number 1. Finally, "uncle" is spelled with the letters "u," "n," "c," "l," and "e" as it is a common noun that represents a relative.