The Child Theme Wizard lets you create a new child theme without the need for additional tools, right from within the WordPress admin interface. Once activated you can find it under Tools – Child Theme Wizard.

Specify a parent theme, customise options such as title and description and click Create Child Theme. Upon success you will find your new theme under Appearance – Themes.

You have the option to include GPL License Terms if you wish. The Wizard will automatically create a thumbnail too.

To find out more about child themes and why they are useful, please read the WordPress Developer Docs on Child Themes.