In some ways, having the manager buffer up the pings is even worse, because then each person has to revive the topic again if they want to have a voice. People don't want to be left out of important conversations, so the only solution is to watch Slack like a hawk all day. The people who spend all day in Slack instead of doing work end up dominating the decision making while the people who focus on work suffer.
Instead, don't hesitate to gather people for a scheduled call after lunch, at the end of the day, or first thing tomorrow morning to clear it up. Record important decisions in a single source of truth that isn't Slack, like your Wiki or ticket tracker.
Treat Slack almost like you would in-office conversations: If you have a spontaneous watercooler conversation about an important topic in-person, you wouldn't go gather everyone involved to come to the watercooler to continue the conversation. You'd send out an e-mail update to others who need to know. Or you'd scheduled a follow-up call or meeting to discuss it.
The in-person rules of communication and avoiding interruption are a good template for how to behave in Slack.