I think I get what you want to do, but am not sure. So I will give it a go.
First off, you really can only have one tab, not multiple ones. If you have more, but only have the dock one icon wide you won't be able to read any of them and they will probably look like crap anyway. So make a new tabbed dock (I think the default will be to be one icon tall, about 6 wide and have 3 or 4 tabs). Remove all but one of the tabs. You know have a dock with one tab, wide and short. Don't dock it anywhere yet. Add whatever icons you want (doesn't matter yet if there are too many to see all). Now, move to the bottom of the dock (opposite the tabs) and you will see a resize cursor appear. Click and drag. This will make your dock wide and tall. Now just go to one of the sides and do the same, but making it narrow. You will end up with a dock that is one icon wide and as tall as you want it. If you need to make it more tall just undock it again and drag on the bottom.
Hope that helps.