Before children can begin to read and spell multisyllabic words they need to get a feel for what a syllable is – for what a ‘mouthful of a word’ is.
If they have had systematic phonics instruction they may find it difficult to switch from sounds (phonemes) to syllables and may confuse the two. Some children need practice in listening out for syllables in words. Teachers mays start with teaching the children to clap the syllables in their names or favourite animals. You can make cards of pictures of animals on one side and the number of syllables of the word on the reverse. The children must clap and count the number of syllables and then turn the cards over to see if they were right. My favourite commercial game is Syllable Safari (see link below). A fun way to reinforce this skill!
P.s. note that older children might be too self-conscious to clap so they may wish to tap the table instead.
You can find this game in many outlets but here is one: