Not *easy*!

Plugin

https://wordpress.org/plugins/woosidebars/

Editing function.php

remove_action( 'storefront_sidebar', 'storefront_get_sidebar' );

Custom CSS

#primary {
     width: 100%;
}

More reading
https://wordpress.org/support/topic/remove-sidebar-on-product-page
https://docs.woothemes.com/document/woosidebars-2/