I need some advice.  I will be making my own wedding cake.  Three tiers of birch tree slices.  I would love to them off center.  But, I've never done a tiered wedding cake this way.  Has anyone? How is it done?  Thanks!

Sure, just place the dowels that are supporting each tier under the section of the cake where you want the upper tier to sit instead of centered on the cake. Don't put them too close to the edge of the lower tier, but as long as the supports are under the cake above it you'll be fine. Transporting it might be fun if it's off-center, so make sure to chill everything before moving it.