I think working with a lateral lisp is one of the most challenging articulation issues that I deal with on almost a daily basis. I have worked with countless materials and I have put together a step by step program that I have had the most success with.
Included are all 7 steps as well as the visual cards needed for each step.
I suggest printing the cards off on cardstock so that they last. I placed all of mine in a portfolio folder that is easy to carry.