In common practice, a new AEM website is generated using the AEM Project
Archetype. https://github.com/adobe/aem-project-archetypeIn the example
editable template template. That's right, a template that you can make
templates with. After building your newly project via AEM Project
Archetype, you will find yourself a full width template under
/libs/wcm/core/content/sites/templates.html/conf, for practice, try
creating new templates in this section from the UI, and this does not
require any coding...