Short answer:
Use actions at the end of the url to change state.
Github does it like this to star a gist:
PUT /gists/:gist_id/star
Explained here
https://developer.github.com/v3/gists/#star-a-gist
Long Answer:
Your objective is making your applications effortless to use an intuitive. Your users should use your app in the simplest possible way. Your users should not suffer the limitations or hard guidelines of the technologies you use.
So actions and operations are inherently not resources, but actions over resources. So they will not respond to a “resource to URI mapping” like REST is.
But you can use the best of REST, and still the best of URIs, combining both.
Remember:
The technology should work for you, and not you for the technology.
If you become an slave of technology, you will end up creating unusable applications or using ugly technologies like XML or Java Home and Remote interfaces, so you end up writing 5 files to create a hello world application.
BEWARE of the “shiny object syndrome”. Google it.
Not because a technology is new or is “the new way of doing things”, it means that is a good technology or you need to get distracted and let aside all other technologies to succumb to REST.
Take what you need from the technology and then make the technology work for you.
Using REST api does not mean you need to discard the capabilities of the URL and URI technologies.
References:
https://www.vinaysahni.com/best-practices-for-a-pragmatic-restful-api#restful