The correct spelling of the phrase "tost a party" is actually "toast a party." The "a" is replaced by "o" to form the correct spelling of the word "toast". The IPA phonetic transcription for "toast" is /toʊst/. The long "o" sound is represented by the symbol /oʊ/ and the "s" sound is represented by /s/. So, to properly toast a party, make sure to spell it with an "o" instead of an "a".