The spelling of the word "rieser" can be broken down using the International Phonetic Alphabet (IPA) as /ˈraɪzər/. The first syllable, "rie", is pronounced with the long "i" vowel sound (/aɪ/), while the second syllable, "ser", is pronounced with a short "e" vowel sound (/ɛ/). The "z" sound is represented by the letter "z" itself, and the final "er" sound is pronounced as the schwa sound (/ə/), which is a neutral vowel sound. Therefore, the correct spelling of this word is "rieser".