The copper is beaten over end grain wood to develope the shape. You will only need to anneal it if it work hardens more than you want. If all you want is a flat panel the work hardening should not be a problem.

Not to sure what exactly you need, but this I know, when copper gets hard from
hammering and you want to soften it up, then heat it up to a dark red and quickly
cool it in cold water.
Konrad

brickeyee, Could I use my Butcher block which is endgrain hardwood or would that be too hard?

Konrad, My sheet is 3' x 4', so a bit large for heating evenly. I assume I would have to heat the whole thing at once. Is that right?

Endgrain softwood is used if you want to develope a texture. If you do it on the butcher block, be prepared to replace or resurface it.
Unless you ned to bend or form the sheet, you are not likely to need to anneal it. Work hardening of a sheet that will be used flat is not much of a problem.

I found a large stump, borrowed a ball pin hammer and beat away. Alas, the texture is nothing like that on my copper sink. We figure it was not beaten. All the thin "walls" separating the dimples are the same width. The shapes of the dimples are not all the same. Some are elliptical, some almost hexagonal. When I beat copper with a hammer my dimples are all the same shape (round) and the walls separating them are random in their widths, depending on how the hammer fell. None are as thin as those I see on my sink. So what is up?
Do professionals use some preformed pattern to press into the copper?

A sheet that size, a bit larger for doing it at home for heat treating.
You could have it done by a Heattreating Facility.
In School, we made some cooper bowls, many years ago, I'm not to sure anymore what we used for, (behind) to beat on.
I think it was lead or sand bag??
Konrad

A ball pen produces a particular look. If it is not what you are looking for, you can try some other tools.
The factory items are done with a planishing hammer (often compressed air powered) and a shapped face.
A hardwood dowel can easily be shapped, then used with a deadblow hammer to create nearly any pattern you want. Use a deadblow to save your arm and shoulder if not using powered equipment. It also tends to give more control for a uniform result.

that's "ball peen", in case you are using a search engine.

Also, a factory "beating" would probably use a method that exactly spaces the blows, to get even dimpling.

Here is a link that might be useful: Merriam-Websters Collegiate dictionary, my fave

help...i had a local sheet metal guy make me a great copper surround for my new wood insert, but he laquered it first, and now with the heat, it is sticky and discolored...how, and what can I use/do to remove it..I don't mind it aging (like me) without the finish...

"help...i had a local sheet metal guy make me a great copper surround for my new wood insert, but he laquered it first, and now with the heat, it is sticky and discolored...how, and what can I use/do to remove it..I don't mind it aging (like me) without the finish..."

Lacquer thinner will dissolve the old lacquer.

You should really use it in a very well ventilated area since it is very flammable, and you want to avoid breathing to many of the fumes. They will give you a splitting headache and worse.