Yes, that is the way to do it. I'm just lazy sometimes. I had twelve MGers at my house today and I took the black background shots just before they arrived. The ribs I grilled were great and they each brought a side dish. I'm so full I just may explode.
I tried to make the dark background blacker with photo shop but when I did, I lost detail on the dark orchid. I only use black poster board with light colored orchids. Also, I see the flash turned the background almost gray. Good rule: don't use flash with a black background.
Jim