First for me in trying to include a template.
How do you go about using what’s in the Zip file in the link below? just recreate the elements (such as a flex container) and add the css file?
Continuing the discussion from Sample Admin template with collapsible side menu:
There’s an offcanvas component available now, so you don’t really need this template believe 
I’m using the offcanvas for the first time on one of my projects, its very easy to use and looks great. I’m using it more than modals now - the offcanvas component only takes a couple of clicks and its good to go, plus there native support for setting button actions for as many offcanvas elements as you need on your page.