You can set a timed reminder on posts made in channels, direct messages, and group messages.
Hover over the message you want to remember, select the More ... option, then select Remind.
Set a predefined delay of 30 mins, 1 hour or 2 hours, delay it to tomorrow or do custom delay for the reminder.
You’ll receive a direct message at the time you’ve chosen, with the body of the message you wanted to be reminded about.
Note that once you’ve been reminded about a message, you won’t receive another reminder unless you set one.