Those were from my first foray into etching! It was fun and easy. I used a rubber stamp and embossing powder (from a craft store scrapbook aisle) to make the resist, melted that with my toaster oven (heat gun works too but can be slow going on a bigger piece), coated the back and sides with acrylic paint, then dropped it in ferric chloride for an hour in hot weather. I cut the circles out with my saw, but I suppose a disc cutter would also work. Then anneal again and dome. I had been concerned that the force required to dome the brass might distort the image, but it was fine. This is 20g sheet and I let it etch pretty deep, and I think that’s probably a good way to start if you plan to form the etched piece after. I don’t know if etching a piece that was already formed makes any difference, but getting the design on would be an issue for me so I default to etching flat.