In Figure 4, I've soldered the center conductor of the coaxial cable to one side of the slot, and the ground (shield or outside) of the cable to the other side. I also solder the cable along the length to the antenna structure. This keeps the cable itself from being a separate radiator - since it is part of the antenna structure the electric currents don't care if they are flowing on the cable or the antenna. This is similar to a balun.