How do I decorate this cake

[oohnewshoes]

I want to make this cake for my dbil's 40th. How on earth do I decorate the cake as a perfect rectangle. I'm guessing a spirit level is involved??

I'm going to make a cookie for the top but the perfect "box" shape is making me nervous.

Getting sharp corners is pretty tricky and takes a lot of practice! There are lots of tutorials and videos on youtube if you have a quick search. Basic tips would be to use ganache rather than buttercream for a crumb-coat layer. Spend time getting this layer absolutely right otherwise your fondant icing on top has no chance of being sharp. I use a dough scraper to get straight edges on my cakes - use a cake card the same(ish) size as the cake top and bottom and use that to guide your spatula or dough scraper to level out your crumb coat. Chill until the crumb coat layer is hard, then when you put fondant on the top, you need two smoothers working against each other along the corners to get sharp edges.
I do use a spirit level to check the top is perfect but it's not essential.

Also are you getting the screen printed onto icing? That'd be my recommendation.

Lizziemint thank you for the reply. I was going to use butter cream but will give the ganache a try.

All your tip are great.