If you are using WooCommerce and Klarna Checkout, along with Shipmondo in Klarna Shipping Assistant, you can offer free shipping with the use of a coupon.
For creating free shipping coupons on WooCommerce, please see this guide.
You can offer free shipping on all desired delivery methods in Klarna Checkout by selecting Free when using coupon.
Follow these steps
Go to settings for Klarna Shipping Assistant on your Shipmondo account: Setting > Integration > Klarna > Shipping Assistant.
Select the desired delivery method where you want to offer the service.
Select Free when using coupon.
Click on Save.