AHi How far in advance can you start to decorate a wedding cake? The wedding is on Sat. Will it be ok if I put the fondant on and stack it today (thursday) and do the final decorating on Friday? Or should it all be done on Friday?

depends on how you are going to hold it and what is inside--if you have used flavors and ingredients that might need to be kept at proper temperature--and if you can keep it at room temp will your recipe not stale out--

so if you answer these comments as if they were questions -- i or someone can probably help you determine that 

best 2u

AThe cake is WASC cake with just buttercream icing. I am going to put a thin layer of fondant on the tiers because the deco is a ruffled rose that is done all in strips and that is going to take me a long time. This is my first attempt to do a wedding cake this involved. That is why I wanted to start on Thurs so I can work all day Friday on deco.

I would think that starting your cake today (thrusday) should be fine..so long as you don't have any fillings that may go off. 

yes i agree with gingerlocks--go for it--good planning there--good luck

 No fillings    Just the icing between layers.      Thank you so much for the help