Jens, many thanks for the reply!
The device name to use is: usbscsi.device (unit 1, at least on my system). It will then show up in HDToolbox, where you can read the device parameters and save it.
Then, from within a Shell window (changing directory to SYS:System) you can format it using UMSD: as follows; e.g.:
Format UMSD: NAME=Greg FFS INTL NOICONS
Be sure to remove the flash drive from your Amiga and re-insert it, forcing AmigaOS to do a "refresh" on the flash drive.
Workbench then shows an Amiga FFS device with the default name of KDH0: which uses 4,096 bytes per block as the default (for my 32 GB flash drive).
HDToolbox, of course, is still slated for an overhaul to straighten out some nuances (nothing new there).
Anyway, here's a link with some photos that I trust will help: