How to make Menthol crystal from mint leaves?
Every recipe I’ve seen asks for mint extract, which is mint that has had the flavors removed by steam distillation. This is not very difficult to do if you purchase some glass distillation equipment from a science supply company. There would be no need to further process it to pure menthol and crystallize. There are plenty of videos on YouTube which demonstrate essential oil distillation. Making crystalline menthol would likely involve solvent extraction, and could produce a toxic finished product if the menthol were not sufficiently dried.

There was a really good answer to the version of the question you asked last week.