The spelling of the word "CRESSAU" can be explained through its IPA phonetic transcription, which is /ˈkrɛ.sɔ/. The "cr" at the beginning represents the consonant cluster of "k" and "r", while "e" is pronounced as "eh" and "ss" represents the consonant cluster of "s" and "s". "Au" at the end is pronounced as "aw". Overall, the spelling of "CRESSAU" closely follows its pronunciation through the use of appropriate vowel sounds and consonant clusters.