When I did this the first time, I managed to get a fairly straight grid, maximizing the number of abodes under influence of the settlement.
However, when it comes to building my second settlement, I notice that all of the adobes have a slight rotation, and they're not evenly rotated, making it a great deal harder to use the settlement efficiently.
No matter how I try, I can't figure out how to deal with this. I've tried dragging them around, against each other and against walls, and I've tried moving the terrain around to "encourage" them to straigthen up. Neither can I find a way to manually rotate then, with some kind of keyboard command.
Here's an image we're I've done my best to show the problem.