Lots of simple box forms, just pin them on the ground, let the angles end up however. Then add the concrete between them and screed over the gaps. The concrete is irregular, but all the squares are not. My question is...is that all one pour? Or is it sprayed concrete like they use for inground pools? I could see a small team with just a few doing this in batches as they go, but I'd be worried about transitions where the batches meet. It'd take a lot of those little forms to do it all in one pour, but I suppose if this is a government roadway project, that's the more likely answer.