I agree that doing it in squares will give a better result. I do lots of "sew and flip", which is a form of crazy quilt assembly. The bigger the square, the bigger the piece of fabric you need to extend from one end to another and the more chance you have of curvature and bubbling. You can find yourself in a situation where the only way to make a piece fit is to cover up a lot of territory already done. This is hard to explain, but if you try it, you will see what I mean.
Dayle