To preface, I understand that this is a fully remote position. I assume that this means your only opportunities to be social with coworkers are scheduled video/phone calls or text chat. I'll assume at least some desire on your part and the part of your coworkers to engage socially. As @NotThatGuy points out, this isn't true for everyone; if a coworker doesn't want to engage socially at work, that should be respected.
Do Not Do This
I personally would be quite annoyed with the practice that you've described - it comes across as disingenuous and at best wastes both our time.
DON'T chat in a way that demands someone's immediate attention. The big advantage of text chat as an asynchronous communications mechanism is that you can juggle dozens of conversations at the same time without interrupting your productivity (like a meeting or a phone call would).
Being Social on Slack
If you want to interact socially with your coworkers on Slack so that it's not a totally transactional relationship, there are plenty of opportunities.
First, there are likely one or more Slack channels for your team that are entirely dedicated to social interaction, often named
#random (see here). This is the right place to talk about the movie you saw last week, or your plans for the weekend, or maybe drop some memes.
Second, many teams end up accumulating interest-specific public/private channels for casual conversation about sports/bitcoin/hobbies/etc. This is a good chance to become better acquainted with coworkers who have shared interests.
Third, if you want to chat with a coworker you have developed a relationship with, then definitely do so. Ask them how their day is going or how their husband/wife/kids are. But only ask them if you are genuinely interested in knowing.
Finally, directly after you have asked a question and had a good back and forth discussion is often a good time for social interaction. Presumably by then you'll have a pretty good idea of whether they're busy or not, and you can easily transition from "thanks for the help!" to "did you have a good weekend?"
If you need to ask a work question, just ask.
DO Explain your whole question at least in summary and leave it for the coworker to respond when they have a chance.
Hopefully you've taken some of the many opportunities to engage socially, so by the time you need a question answered there's no need for a rote formality.