A bad example from Ellejamilla:
They don't have any prominent sections with delivery information. No messages at the top of the page, no dedicated sections near the ATC button. The only info about delivery is placed in the collapsed tab below the ATC section, but most users will never click there.
A not very good implementation from Aloyoga:
They have a free shipping section right below the button, but it's not clear whether they deliver to my country and how fast it is. That is, the user has questions and every question that he can't find an answer to is a potential reason to leave your site. Moreover, if you click on "Read more" text, it will send you to another page in the same tab, which is a very poor user experience, because users will need to go back and forth between pages.
A good example from Amazon:
Amazon shows 2 notifications about delivery to New York (below the search bar and the ATC button), also it shows that if I order within 6 hours, it will be delivered to me today. Playing with urgency elements.
A good example from Gymshark
They have a dedicated section about shipping with information about standard and express delivery and also additional info about the time of delivery in the collapsed tab "Delivery & Returns".
A good example from Fashionnova:
They have 2 sections about delivery: static message below the header about free shipping on orders over $75 for US and Canada Shoppers and additional info about estimated time of delivery and "ships within hours" text right below the ATC button
A good example from a Shopify store:
There are 2 geo-targeted notifications: the sticky bar at the top and the shipping section below the Paypal button. As a result, it's absolutely clear for potential customers from the UK that they get free shipping on orders over $50.
If you are still unsure about this guideline, you can check Baymard's article, where they go deep about it. And here's another good read where they explain why placing just a free shipping banner in the header is not very effective.