This plugin Child Theme Configurator helps us to create child theme easily. Here is some quick steps:
1. Install & activate that plugin
2. In Admin menu, click on Tools >> Child Themes
3. Select the parent theme, name the child theme, and select other options:
then click blue button at bottom of page.
4. , please skip this step.
Otherwise, please click on Files tab to copy relevant files from parent theme to child theme:
It all depends on your need to select what files to copy. If you only want to replacing layout in Category page, you should select category or archive. If these 2 files were not existed, please select index.
5. Finally, activate this child theme on Themes page.