The spelling of "Castlet" may seem unusual, but it can be explained through phonetics. The IPA phonetic transcription for "Castlet" is /ˈkæslət/. The first part of the word, "cast," is pronounced with a short "a" sound and a "t" at the end. The second part, "let," is pronounced with a schwa sound (the vowel sound in "the") and another "t" at the end. When combined, the word is spelled "Castlet," which may be unfamiliar at first but can be easily pronounced with the guidance of phonetics.