This is an accepted solution.
Julie here from Shopify Support.
Offering customers free gifts if they purchase a certain amount is an excellent incentive and a great way to increase your total sales.
I appreciate you sharing this example. Using Chrome DevTools, I can see that there is some code from Loyalty Lion's Loyalty, Rewards, and Referrals app present. This app allows merchants to offer customers free gifts with their purchases, and also includes a ton of other great features, like loyalty programs, custom rewards, the ability to create early access sales, and much more. The Loyalty Lion developers have some information on how to use their app to offer free gifts here.
There are also a few other similar apps in the Shopify App Store that allow you to offer free gifts. Aside from Loyalty Lion's app, some popular options include:
These apps have great reviews and sound like they offer exactly what you're looking for. I suggest exploring some of those options and seeing which suits your needs the best. In each app listing, you'll notice some screenshots and a link to an example store, so you can see what the app looks like in action. You'll also notice a Support section, where you'll see a link to their FAQs and contact information for the app developers. Should you have any questions about any of these apps, you can always reach out to the developers directly.
I hope this answers your question and I'd love to hear more about the free gift promotion you plan on running!