Turn off all notifications, and let everyone else know that Slack is not the way to reach you if there's an urgent need. Unless, of course, it's your employer'

Turn off all notifications, and let everyone else know that Slack is not the way to reach you if there's an urgent need. Unless, of course, it's your employer's policy to be promptly responsive on Slack, in which case I'd try to change that or consider other jobs if you're required to be constantly "on-call".