I would recommend you check with each and every student in your class whether they know how many syllables are in [add word]. You’d be surprised how few can do syllables with automaticity and yet, it is one of the easiest ways to work out spellings and make the prospect less scary.
Students who have been taught can be seen tapping their foot under the table, their pen on the table or clapping their hands to work out the syllables; for some it comes naturally, for others it can take a while to get it.
A bit like rhyme, there are some students who find syllables really difficult – the evidence for a correlation to this and reading difficulties is slight (I think) but the ability to reflect upon and manipulate the sound structure of words (phonological awareness) is a skill which will help with reading and spelling.
What is a syllable?
Quite simply, a beat of a word.
An-ti-dis-est-ab-lish-ment-ar-i-an-is-m … 12?
Most syllables have a vowel or vowel digraph (two vowels together making one sound ai, oa etc) and that is worth knowing for students when spelling. Chunking a long word into syllables can help to make spelling easier.
That said, there’s this and it’s an excellent article on exceptions such as prism or words which, while they have a vowel sound, it is not stressed.
When teaching new vocabulary, I would include syllables as part of the introduction after meaning. Phonics first, then syllables including vowels, similarly spelled words using rhyme if required, etymology of word, other words which mean the same and using the word in a sentence.