@Alvaro - Have you already reviewed the Step-By-Step documentation form Checkout X?

https://help.checkout-x.com/en/articles/4156215-setting-up-klaviyo

Checkout X provides two events (metrics):

• Checkout X - Email Filled
• Checkout X - Order created

Make sure you see those events coming into Klaviyo.  Go to Analytics → Metrics and look for those two metrics above.

The key here is to understand that all people who complete the first step of the checkout process will send to Klaviyo the first event “Checkout X - Email Filled” and if they proceed to place an order, they will get the second event “Checkout X - Order Created.”  What we are trying to do is if they do the first step but don’t complete the order in a given time, we want to send them a message.  But if they do complete the order, then they will have get “Filtered” out and not receive the message. 

To create your Cart Abandonment Flow,

• Make a “Flow” triggered by Metrics, where the trigger should be “Checkout X - Email Filled”
• Create a Flow Filter of “Order Created” zero times in the Last 30 Days (or X Days) to avoid people from getting this email consecutively in a short period of time.
• Add an initial Time Delay so you give someone ample chance to complete the Order before getting their first abandoned cart message.  You can try different time delays, but anywhere from 30 minutes to 4 hours would work.
• Then add your Message and edit it as you normally would to create a message.  Now, inside the template, you’ll need to use Dynamic Variables if you want to populate the message with the items they abandoned.  Since Checkout X will provide the data in their own way, you may have to map them correctly.  The step-by-step instruction has a video to show how to do this!
• You can also add additional Messages with more time delays if you’d like.  For example, you can send a second email after a 1 Day delay if they still have not placed the order.

Hope this helps!