The spelling of the word "Ostynn" can be explained using the International Phonetic Alphabet (IPA) transcription. It is pronounced as /ɒs.taɪn/. The "O" is pronounced as the short vowel sound /ɒ/, the "st" combination is pronounced as /st/, and the double "nn" is pronounced as /n/. The "y" is pronounced as the diphthong sound /aɪ/. Therefore, the correct spelling for this pronunciation would be "Ostine." It is important to use correct spelling to avoid misunderstandings and miscommunications.