Completely new to magento 2. Just installed magento CE 2.0.9 with no sample data. All the articles I've read say to base custom theme on, say, blank you have to create vendor/theme in directory app/design/frontend where there is supposed to be Magento/luma and Magento/blank. However, in my installation the Magento folder is completely empty in app/design/frontend/Magento. Have I missed something during installation? I've installed Magento by uploading to my server, unpacking it, and running the web-based Setup Wizard. I can see my theme in Admin but it does not show any parents although in theme.xml I've stated 'parent'Magento/blank'/parent'. With Magento 1 I was able to create a custom home page by copying folders and files from parent theme into my theme and altering them. How can this be done here? Many thanks for your help.
However, in my installation the Magento folder is completely empty in app/design/frontend/Magento. Have I missed something during installation?
No. Usually the folder will be empty after installation.
By default, theme files will be available on <root directory>/vendor/magento/theme-frontend-blank directory. You can copy all the files in the directory and place it in your theme(app/design/frontend/Vendor/Themename/). Make sure parent theme is configured in your theme.xml like below
So now you can modify your changes in your theme files.
I suggest you simply follow the official developer documentation. I was able to create a theme from scratch just with this series, so give it a shot: