The spelling of the phrase "wast back of" can be a bit confusing at first glance. However, with the use of the International Phonetic Alphabet (IPA), we can break it down phonetically. "Wast" is pronounced as /wɑst/, with a long "a" sound in the first syllable and a short "a" sound in the second syllable. "Back" is pronounced as /bæk/, with a short "a" sound followed by a hard "k" sound. "Of" is pronounced as /əv/, with a short "u" sound and a soft "v" sound. Together, the phrase is pronounced as /wɑst bæk əv/.