Public Slack

This is a simple PHP page that you can direct people to sign up for your Slack group, without you needing to personally send out invites.

Here is an example of what the page looks like.

Setup

You need to find your Slack authentication token for sending invites. Here is how to find it:

Sign into your Slack group as an Administrator.
Go to your team invitation page: https://example.slack.com/admin/invites
Open up the developer tools in your browser, and select the Network tab.
Invite a member. You can enter a fake address.
In the developer tools, find the request that looks like users.admin.invite?t=1111111111
Scroll down to the bottom of the request and find the Form Data. Write down the information in the channels and token fields.
In the config.php file, enter the information you wrote down in step 6. Set slackAutoJoinChannels to the channels field, and slackAuthToken to the token field.
Also put your Slack group name under slackHostName. It should be the same as group name in your Slack URL.
Set the contact information, which will be used in the signup page if people are having troubles.