How to Use Flat Rate Boxes with WooCommerce USPS Shipping Plugin

Customer :

Trying to configure the USPS Flat Rate boxes sm, med and large. The documentation says they are hard coded.
I have Yes, enable Flat Rate services. What settings do I need to enable to have these 3 boxes? We actually Only use these 3 US Mail flat rate boxes for shipping along with UPS options.

Support :

We have provided an option to select Flat rate boxes in USPS plugin in the new version.

Kindly download the latest version of the plugin by logging onto elextensions.com –> My Accounts.

Once you install the new plugin, you can select only the three boxes – US Mail Priority Flat rate SM, Med and LG boxes using the field “Flat Rate Boxes“.
Remove all existing boxes that you had configured previously from the “Box Dimensions” tab.

The plugin will now directly pick the product dimensions and then match with the boxes selected by you in the Flat rate boxes and fetch those rates.

I tried to replicate your case on our test server and correctly got the rate $6.80 for small flat rate box.