Make sure to update the BIOS if you have not. There was some USB flash drive compatibility issues on that mobo.
Can you see the USB drive in the BIOS Boot device priority bar?
Besides moving the device icons to change the boot priority, you could disable everything but the USB flash drive.
After Windows is done with the setup and reboots you get into the BIOS and enable the Boot drive.
Also, set Legacy USB Support to 'Auto' under USB Configuration in the BIOS. It will automatically detect if any USB device is connected.