AHi if you cover a cake board fully in icing and leave it to rest for a day or two to harden up would you ice your cake and then transfer it straight away to the board? I tried this but it cracked the fondant in the cake making it look mottled - I was wondering if there's a better way?

Did you have the cake on it's own cardboard?

I don't often cover the board before icing the cake - you really need to leave the cake to firm up overnight before moving otherwise you will mark the soft icing.  I much prefer to place the uniced cake on the board and roll out the paste large enough to cover cake and board all in one, using the right-angled side Edger to smooth the sides of the cake and board together.  You don't need to place the cake on it's own hardboard, just set it directly on the drum.
 

I cover the board in fondant a day or two in advance. Then have the cake on its own board, cover in fondant, leave for as long as it takes me to cover other tiers in fondant, or not at all, and transfer it directly onto the fondant covered base board.

Then the fondant on the cake is still soft, and you can smooth any edges back down if they get a bit messed up.

if i am going to do this i will build the cake on the drum as usual, but then cut pieces of fondant for the 2-3" surface to the edge of the board.  I will put a ribbon on the edge. I'll put some tylose or CMC in it to harden it up a bit.