Here are useful links to websites

How to say S and Z
This link will take you to a you tube video tutorial with helpful suggestions on how to say /s/ and /z/ sounds - both frontal lisp (substituting a 'th' sound) and lateral lisps (airflow escaping out the side of the mouth instead of coming out of the front). 

**External Website - clinking on the link above exits the PWCS website, however it should open in a new tab at the top