Let's perform the following steps to automate the Docker image build directly from our GitHub repository:

1. Sign in to your GitHub account.
2. Select a repository where you have maintainer access. In our example, we are using the fork of the k8sdevopscookbook/python-flask-docker project.
3. Click the Actionstab.
4. From here, click on Add a new workflow.
5. Create a dockerimage.yml file under the .github/workflows directory with the following content:

name: Docker Image CI
on: [push]
jobs:
  build: 
    runs-on: ubuntu-latest 
    steps:
    - uses: actions/checkout@v1
    - name: Build the Docker image
      run: docker build . --file Dockerfile --tag my-image-name:$(date +%s)

The workflow will create a new Docker image every time new code is pushed to the repository.