Pastrami starts with a brining process, commonly called corning. Once you've corned the roast, you have the option to braise/boil it, or smoke it into a pastrami.
Rub it thoroughly over the corned roast, getting a nice coating.
When it's up to temp, let it cool, then slice up for sandwiches. I usually wrap it in foil, and toss it in the fridge till the next day when I slice it.