Here's a breakdown:
* ˈɒf: The first syllable is a short "o" sound, like in "hot" or "lot".
* ˈɔːf: In some dialects, the first syllable is a longer "o" sound, like in "law" or "caught".
* .ən: The second syllable is a short "en" sound, like in "pen" or "ten".
So, "often" is pronounced with a short "o" followed by a short "en", or a longer "o" followed by a short "en".