That’s how I did it except mine came with a 32Gb chip and came from Ali for $14
I’ve never done it but I’m told You CAN flash on the board once you figure out the secret to get it to boot from USB.
Easiest way is with a USB keyboard. You have to use Etcher on your PC to expand the OS onto a USB drive. Then you need a copy of the .img on the same or 2nd USB drive. Boot from the USB then copy the .img onto the EMMC