To me self work is choosing a small attainable goal that is aligned with the larger framework of my belief system (beliefs about myself and how I operate in the world around me) that when satisfied/accomplished changes my internally so that when I encounter the same or similar scenario in the future I no longer act as I was but act in the new way I have set out to develop for myself. Essentially the process of death and rebirth at a very small, practical scale.
I can give you a concrete example. Whenever I was attempting to overcome my social anxiety I noticed that it was difficult for me to maintain eye contact with people during casual conversation, particularly while I was in turn speaking. So, I would set the smallest goal possible to change my behavior: I would just attempt to notice when I looked down or away while I was talking, and once I noticed, shift my gaze back to making eye contact and continue speaking while holding the eye contact steadily.
It didn't matter how long I did it for, whether 1/2 a second or one minute. It only mattered THAT i did it, and so I could use that moment of success as a frame of reference to begin rebuilding myself in future encounters similar to that, so that I could begin to experiment getting better and better at holding eye contact for longer periods, eventually to the point where I no longer had to do it consciously but instead it became an unconscious behavior which ultimately align with the larger framework of how I believed I wanted myself to operate in the world around me.
So to me that is what self work is, in a nutshell, choosing something you want to improve about yourself and taking specific action with clear outcomes to execute on the improvement.