It requires discipline to say "sorry, can't help you" and to accept that response and go back to working on the problem on your own.
1 - Do ask questions through Slack, etc
2 - Do make sure you're responsive and if you're not don't complain people come and ask you directly
More important is to understand how async communication works. Otherwise, you have to create a physical boundary (remote work) to enforce this.
That's why I still fundamentally prefer e-mail (with a sensible set of mailing lists and an easily browsable archive) for serious decision making. IRC or Slack are great for building a community atmosphere but best reserved for more ephemeral things.
Also anyone that needs to be in a conversation is in the Slack already. File sharing, code sharing -- all that is much easier than email. With Threads -- conservations are more focused and organized. In-chat images are also super simple (as opposed to sharing actual images or links to images that require clicking as in email.)
I despise email and hate phone calls even more.
I think the 'problem' with Slack is how some people use it. The 'expectation' of a quick answer isn't Slack's fault.
Of course. Nearly everyone prefers just walking up to a colleague.
However, nearly everyone also prefers that colleagues not just walk up to them.