If you want to increase your AOV (Average Order Value), you can definitely start from the WooCommerce Checkout page.
A client asked me to place a “Donation Area” close to the “Place Order” button (so at the bottom of the page, once customers are ready to pay) to drive more awareness around this add-on. All I had to do was creating hidden products with a donation value, use my own “Custom Add to Cart URL” guide to create add to cart links and print an HTML box right above the checkout button by using my WooCommerce Visual Hook Guide for the Checkout Page. Enjoy!
How to show an upsell / add-on area @ WooCommerce Checkout (suggesting to add more products to cart)
PHP Snippet: Show Add-Ons Area @ WooCommerce Checkout Page
Requirements:
Product IDs you want to add to Cart (14877, 14879, 15493 in my example)
No “redirect to Cart after add to cart” option checked in WooCommerce settings