This was one of the main concerns about moving to Slack in the first place, so I understand the question. However it turns out there are a couple of ways to handle this that I think are pretty simple and relatively unobtrusive.
One way is to download the Slack app for your phone, if you have a smartphone, and set it up to give you notifications. That way you’ll be pinged if something gets posted (you can adjust what events cause a notification, and shut off notifications if needed).
Another way is that you can configure Slack to send you email notifications of direct messages or mentions. Here’s the official page with instructions: https://get.slack.help/hc/en-us/articles/201649273-Email-notifications Note that this does NOT send you notifications just of any posting whatsoever, just if someone messages you or mentions you directly. Those would be the notifications that typically you would want to respond to the most quickly. Then, for regular postings, if it were me I would set a recurring reminder on m