Slack "channel create" button sometimes does not appear

When opening the Slack glance panel, the "create channel" button is sometimes missing. On some occasions it does appear, but the channel name input box can't be selected with a mouse because it's covered by another element - the only way to edit it is to tab to it using the keyboard.

Here's an example when the "create channel" button doesn't appear on Safari:

Workaround: 

Close the Slack glance panel and re-open it.

Original issue:

Reported by scullinan via email:

Creating a Slack Channel does not work in all browsers including safari all the time