This is the situation, I'm going to create a promotion in which the item is free, but I'm charging shipment for the item. I want the shipment rate to be for a specific item. The way I was trying was setting a weigh to an item and then match that weigh to a price. Example:
Weigh 8lb - Price 8$
So if 2 items get added to the car, ideally that would multiplicate making it 16. Problem is if I want to use weights with that, I'd have to create an amazingly large list.
Using the Courier API I think is discarded because I don't have a backend to provide a rates response. So... What I'd like to do is to directly update the shipping rates of shopify that you manually set, through the API. That would help me save an incredible amount of time. So the next problem is, I don't see any PUT/POST request available for that here: