Build the word one letter at a time.
Word Builder shows a picture and asks the child to spell what it is, either by tapping letters in order or by filling in the one letter that is missing. Spelling by construction rather than by multiple choice means the child has to hold the whole word in mind, which is the part that transfers to writing.
The 5-7 level shifts the balance towards building words from scratch, with missing-letter rounds mixed in as a break. This is the level that lines up with early phonics work on consonant-vowel-consonant words.