To activate the USPS Flat Rate Boxes, go to the Boxes Section in your Dashboard.
Here you can activate the different boxes to be selected manually or automatically.
If you enable them to be automatic, the Easyship algorithm will automatically apply the best available box for you depending on the cost of shipping.
Note that you need to have synced all your item dimensions in The Products Listing Feature
About USPS Flat Rates
When selecting these boxes, please note that USPS requires specially marked boxes that are sold by USPS. Please also note that all contents must fit comfortably and packing must be sealed without any convexity/curvature.
Provided that all your commodities fit into a Flat Rate envelope or Small boxes, USPS Flat Rate will always be available at a lower rate compared to USPS Regional Rate boxes. This is across all weights (up to 70lbs) and zones.
Yet, Regional Rate boxes are more closely sized to the Flat Rate Medium and Large boxes and the different services have distinct advantages.
Flat Rate boxes (Medium and Large) are a better option when shipping further. Regional Rate boxes (A and B) will offer the lower price for shipping between closer destinations.
The key restriction of Regional Rate boxes is that their contents may not exceed 20 lbs, depending on the box option. In contrast, Flat Rate services support content up to 70 lbs.