I have an order for a 12 inch square cake, covered in buttercream. The decoration on top is to be a single word, with the first letter "K", in fondant, measuring about 8 inches tall and 4 inches wide.

How is best to make and then transfer it to the cake? As it will be placed on buttercream, I really only have one chance to place it without having to re-do and smooth the buttercream again, if I get it wrong. Should I make the "K" with tylose and fondant, wait until it hardens and place it - or is it likely to crack, being quite large? Or maybe place when still a little pliable to prevent cracking, but risk edges of the "K" being not quite straight.

Thanks :)

Make one K in fondant and one in paper. Use the paper template to line it up on the cake and mark with a toothpick for straight placement and spacing. Then drop it in place where you marked it (marking it just inside where the letter goes so the fondant letter covers your marks). 

Fantastic idea! I'll be creating my own stencil/template for the letter anyway, so will keep the part I cut out as my guide. Thanks :)

Would definitely wait until fondant letter dried or use a bit of tylose. It's so much easier if it's not all wobbly.