Im worried it wont look neat around the square edges. Would it help to use royal icing to hold it to the cake? I use crusting buttercream, and the ribbon doesnt stick well to it.
I did a square one (in my photos) and to get the corners I ironed the corners. They would not go around the corner straight without smashing the edge so I decided to try this and it worked great for me. It was a little bit of a pain, had to iron one corner put on then measure the next...iron. I did it this way to get the corners exact. I tried just measuring the 12" then 12 more but didn't quite work. Then just used a dab of buttercream and a big floral pin in the back to hold. When I got there with cake, they wanted the pins all around and it held it in place. Hope this helps.