The correct spelling of the word "blankest" is [blæŋkɪst]. The word is formed by adding the suffix "-est" to the base word "blank". The "e" in "-est" is added to provide a smooth transition between the consonant and vowel sounds. The "k" in "blank" is followed by a short "e" sound, which is represented by the letter "e". The final "t" in "-est" is pronounced with a slight puff of air. Overall, the spelling follows the standard English phonetics.