There are a few different ways to automatically send a Google Doc when a new channel is created in Slack, depending on your specific use case. Here are a few options:
Use the Slack API and Google Drive API to create a custom integration. When a new channel is created in Slack, the integration can automatically create a new Google Doc in your Google Drive and share it with the members of the Slack channel.
Use a third-party tool like Zapier or IFTTT to connect Slack and Google Drive. These tools allow you to create “zaps” or “recipes” that trigger actions in one service based on events in another service. For example, you could create a zap that watches for new channels in Slack, and when one is created, creates a new Google Doc and shares it with the members of the Slack channel.
Use Slackbot to automatically create a message to the channel with the link of the Google doc.
Create a custom bot (using Botkit or similar) that can listen for specific events in a channel and respond with a message. A bot can be programmed to listen for the creation of a new channel and immediately post a message with a link to a Google Doc.