The phrase "most moss grown" is pronounced as /moʊst mɒs groʊn/. The first word, "most," is spelled as expected, but the following words may require a closer look. "Moss" is spelled with double s's, as most other English words that end in 'ss' are pronounced with a short vowel sound. The word "grown" is spelled with an 'o' instead of an 'e' due to its historical roots and evolution. Overall, the spelling of this phrase adheres to typical English spelling conventions.