I tried multiple times. Oh, the frustration! So, I sat there a bit and thought about it. All I knew about stamping (I am not an expert, obviously) and figured out that I needed to stabilize the metal with the stamp. And only having two hands was part of the problem.
So I used some blue tape and tried that on the bench block. I still did not have a good solid impression.
Next up, I taped the copper and stamp together and put it in my vise. That way, I could just hold onto the metal and hammer away.