I don't have an idea about Global E, but if you are planning to use FedEx to handle shipping, the FedEx Rates, Labels & Tracking app can solve this issue. The app allows you to handle volumetric weight as well.
The app has three packaging methods; weight-based, pack items individually based on weight and dimensions, and box packing. You can add the weight and dimensions of your products and select the packing method according to your choice. Now, the app will automatically select the box based on these values and calculate the rates accurately.
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