I cannot recommend enough cultivating a reputation for being grumpy but fair. Try and make approaching you like a game of Dark Souls; rewarding if the player is prepared. People will respect your time and accept death as the penalty for failure.
"If you work with the door closed, you won't be interrupted - you get your work done. You work with your door open, people come by and stop and chat and so on, so on but I've noticed very clearly at Bell Laboratories those who work with door shut may be working just as hard ten years later but they don't know what to work on. They are not connected with reality. Those who have the door open may very well know what's important. I cannot prove to you whether the open door causes the open mind or whether the open mind causes the open door. I can only establish the correlation and it was quite spectacular. Almost always the guys with the door closed were often very well able, very gifted but they seemed to work always on slightly the wrong problem."
For those discussing DND elsewhere in this thread, the notion of being generally reachable at specific times exists.
Call if its an emergency, and its probably not really am emergency for me if you don't have my number
I am using same rule and my slack is very quiet while colleagues are constantly complaining of distracting messages.
They also don't chitchat anymore knowing that unimportant inquiry will be left unresponded for a while, giving them anxiety