AHi I have a question... For a tiered cake I have seen people using straws and dowels to support each layer... What do you put the tiers on? Is it a thin cake board cut to shape?? Thanks holly

Generally, yes, you'd use a board under each tier cut to size.  However, some people don't do that, especially if they're using fondant.  You may see some people just spread royal icing in between each tier.