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.
You can use the Multi Carrier Shipping label app that allows you to define product dimensions. In addition, you can define your own boxes in which those products can be packed based on multiple algorithms like :
- Stack First : This allows you to stack items one on top of another
- Volume based packaging : This allows you to pack items based on volume
- Dimensional weight : This uses the existing dimensions of products to calculate dimensional weight. The algorithm compares the actual weight to dimensional weight and sends the higher one for rate calculation.