Is there a way to flash or copy files to a Rock-PI right after flashing an image?

Hi,

is there a way to copy or flash a file on a Rock-PI, after i have flashed my Rock-PI?
I would like to copy some files right after i flashed an image with RkDevTool on Windows, without booting the rock-pi.

I was thinking about making a small paritition image, copy the data into that partition and flash that image after the actual image flashing. But i’m not sure, what offset i would need to use in RkDevTool. Do i need to flash a gpt partition to let the rock-pi know there is a new partition?