You can connect your Google Calendar account to Gonebusy in order to have access via Slack in a few easy ways:
Method 1 – If you're the first person on your Slack team to install the Gonebusy app, just visit www.gonebusy.com, click on the Add to Slack button, and follow the prompts. (Even if you're not the first person, this method will always work.) After successfully adding to Slack, Gonebusy will message you in Slack with further instructions.
Method 2 – If you already have an account on Gonebusy, just visit your Account tab and click on Google - Connect Calendar.
Method 3 – If someone on your Slack team has already added the Gonebusy app, you can type
/gonebusy help and select the Connect my Google Calendar from the dropdown of available help topics.
Method 4 – The first few times you are invited to a Google event by someone via Slack, you will be prompted to "Connect Your Calendar". Follow the link to connect your Google Calendar on www.gonebusy.com. After the first few times, Gonebusy will stop asking you. Because we don't want to be annoying :-)
Once you've connected your Google Calendar, you can now take advantage of all that Gonebusy offers in Slack: book and create events, invite your colleagues, view your schedule, setup automatic status sync – the list goes on.