Tips:

• Pronounce the letter “o” as
  /ɔ/— like the sound of disappointment, Awwwww! Do not pronounce this vowel as /o/,
  /ɑ/, or a Noo Yawk-style [uɔ].
• Pronounce this word as two syllables—not one syllable [ɔfs] or three syllables [ɔ fə si].
• Pronounce the vowel in the second syllble as the weak schwa vowel
  /ə/ and not as
  /ɪ/ . Further, be sure to voice the schwa vowel
  /ə/, which occurs between two unvoiced consonants
  /f/ and
  /s/.