The spelling of the word "FLEN" is unique and requires the use of the International Phonetic Alphabet (IPA) to explain. The first sound is an "f" sound, represented by the /f/ symbol in IPA. The second sound is the vowel "e", represented by the /ɛ/ symbol in IPA. The third sound is the consonant "l", represented by the /l/ symbol in IPA. The fourth and final sound is the vowel "n", represented by the /n/ symbol in IPA. Together, these four sounds create the unique spelling of the word "FLEN".