Flat Able Bootstrap 5 Admin Dashboard is like the superstar of admin templates among many others out there. It's super special because it has a ton of pages and tools that are really helpful.
Demo: https://themeforest.net/item/flat-able-bootstrap-4-admin-template/19842250
FlatNews is one of the most flexible responsive editorial and magazine Wordpress themes. This theme is very easy to work without touch to code.
Demo: https://themeforest.net/item/flat-news-responsive-magazine-wordpress-theme/6000513
SIMPLICITY is an creative flat retina WordPress theme.
Demo: https://themeforest.net/item/simplicity-creative-flat-retina-theme/5477244
Create easily your own flat and responsive visual tours on your wordpress website. A tour is a sequence of text, tooltips and dialog windows that guide the user, even through the different pages of the site.
Demo: https://codecanyon.net/item/wp-flat-tour-builder/7981938
Advanced Flat Rate Shipping Method for WooCommerce is a fully featured plugin for all your flat rate shipping needs.
Demo: https://www.thedotstore.com/flat-rate-shipping-plugin-for-woocommerce/
Sell any customized services and products with ease by creating your own flexible cost calculator or payment method (even with a subscription!) On your PHP website.
Demo: https://codecanyon.net/item/php-flat-estimation-payment-forms/10550735
This is not a standalone script. It is a backend theme (staff-admin area) for Perfex CRM. Flat Admin Theme for Perfex CRM, redesigns the backend’s experience by adding flat aesthetics at your staff’s interface.
Demo: https://codecanyon.net/item/flat-admin-theme-for-perfex-crm/24754675