The correct spelling of the phrase 'most constructing' is actually 'most constructive', and it is pronounced as /məʊst kənˈstrʌktɪv/. The IPA phonetic transcription breaks down the pronunciation into individual sounds, with 'most' pronounced as 'məʊst', 'constructive' pronounced as 'kənˈstrʌktɪv', and the emphasis placed on the second syllable of 'constructive'. It is important to use the correct spelling and pronunciation of words to effectively communicate and avoid confusion.
The phrase "most constructing" does not have a specific etymology as it is not a recognized English word or phrase. It seems like a combination of the adjective "most" and the verb "constructing" with the superlative form. However, without additional context, it is difficult to determine the intended meaning.