I have applied for a Canada work authorization visa from the United?
Yes you can, the passport stamping is done upon entry to Canada, they will direct you to secondary inspection and there they stamp your passport with a entry validity , as well as to print out your work permit paper. But make sure to check the written conditions on that work permit are correct, they make mistake all the time, otherwise, you may need to exit Canada and re-enter again to ask for correction or that written content, usually it is done by going through U.S border.