FedEx One Rate
If you are enrolled in FedEx One Rate program, you can choose to use it in Teapplix.
FedEx One Rate is applicable to some of the FedEx ship method such as Priority Overnight, 2Day, Express Saver, etc. And you have to use one of the FedEx package type.
After you set the right ship method and weight on an order, you need to click on the Rate&Options link, select one of the FedEx package type, and click on the Advanced Options tab. You should see a checkbox to enable FedEx One Rate for that order. If you don't see such a checkbox, it would mean the ship method or the package type you choose to use does not support FedEx One Rate.