First, familiarize yourself with the xkcd API. The xkcd website provides a simple JSON API. Each comic's data can be accessed via a URL like `https://xkcd.com/[comic_id]/info.0.json`. This JSON data includes fields such as title, image URL, and alt text.

Set up a development environment with the necessary tools. You'll need a programming language that can handle HTTP requests and JSON data, such as Python. Ensure you have access to libraries like `requests` for making API calls and `google-cloud-pubsub` for interacting with Google Pub/Sub.

Write a script to fetch data from the xkcd API. Use the `requests` library to send HTTP GET requests to the xkcd API. Parse the JSON response to extract the data you need. Here's a basic example in Python:
```python
import requests

def fetch_xkcd_data(comic_id):
url = f"https://xkcd.com/{comic_id}/info.0.json"
response = requests.get(url)
if response.status_code == 200:
return response.json()
else:
raise Exception('Failed to fetch data from xkcd.')
```

If you haven't already, create a Google Cloud account and set up a project. Enable the Pub/Sub API and create a Pub/Sub topic where you will publish the xkcd data. Ensure you have the necessary permissions to publish messages to this topic.

Download a service account key from your GCP Console and set your environment variable `GOOGLE_APPLICATION_CREDENTIALS` to the path of this key file. This will allow your script to authenticate and interact with Google Pub/Sub.

Use the Google Cloud Pub/Sub client library to publish the xkcd data to your topic. Here's a basic example using Python:
```python
from google.cloud import pubsub_v1
import json

def publish_to_pubsub(data, topic_id):
publisher = pubsub_v1.PublisherClient()
topic_path = publisher.topic_path('your-project-id', topic_id)
message = json.dumps(data).encode('utf-8')
future = publisher.publish(topic_path, message)
future.result() # Wait for the publish call to be complete
```

Automate the process by integrating the fetch and publish scripts. You can use a scheduling tool like `cron` to run your script at regular intervals. This ensures that new xkcd comics are fetched and published to Google Pub/Sub as they become available. Be sure to handle exceptions and log errors for troubleshooting.

By following these steps, you can effectively move data from xkcd to Google Pub/Sub without relying on third-party connectors or integrations.