Sometimes I also use the HTML snippet, but i never did these steps for it to work:
I followed below steps to use HTML Snippet
Copy all the custom .js files to theme/js folder
Copy all .html files to theme/html folder
Copy all .css files to theme folder.
Its probably not this but its good to know anyway, html and javascript snippets are also "translated" by the modeler. Which means that if you change your code in one langauge you have to do the same in the other language otherwise it wont work in that other language. I know its super weird but I've had that problem a few times.
I also never had to do the steps you mentioned, the snipper works out of the box.