These are my standard "defensive line" blueprints.
The laser-only blueprints are good for the early-to-mid game. Once I have a personal roboport, I can quickly throw these up anywhere that I need a wall. The asymmetry of the "corner" blueprint is intentional: It allows constructing rectangles without breaking the pattern.
I recommend building these walls so that the turrets are aligned with the railroad grid, so that rail lines may be sent through the wall with a minimum of disruption.
The "heavy" blueprints are designed to be dropped in-place over the laser-only blueprints. They provide a defensive line sufficient for the late game (at least in vanilla), when paired with a logistic network for supplying ammo, as well as a supply of fuel for the flamethrower turrets. (I recommend light oil.)