How to Add Slashes to Static Pages' Slug

In WordPress, I'm trying to organize Static Pages to appear to be in a subdirectory URL structure. For example, I have static pages for cars like: bmw, ford, chevy, dodge, jeep, etc. I want these static pages to appear to be in a subdirectory (/cars/) like this:

/cars/bmw/
/cars/ford/
/cars/chevy/
/cars/dodge/
/cars/jeep/

If I try to edit the slug for the static page named "bmw" to this: /cars/bmw/... WordPress changes the slug to this: /cars-bmw/

In my research, I found plugins that can add categories for static pages, but I do not want this solution as these are not "categories" and I do want these static pages displayed on category page - or treated as categories. Editing the permalink structure does not seem to work either because there will be other level one directories like "/boats/" - for example. These level one directories will be different in some cases.

The question is how can I add slashes to a static page's slug? Or, some other workaround that really works in my situation.