You be direct. When people come to you and interpret you, say “I am currently working on something else, but I will come find you when I’m free”. Most people eventually pick up that IM’ing first wastes less of their time.

If you constantly give them your attention immediately, you are telling them that’s how it should work.

then come the hour long "it's easier if we just hop on a meeting" invites or dreaded "hi" messages because many of the same people who aren't considerate about interruptions are allergic to async communication