The original A1 "birdcage" FS had slots all around, and therefore didn't need to be aligned in any special way.
When the A2 FS was designed (with the bottom slots closed), it was necessary to align the FS so that the closed portion was at the bottom. To do this, a peel washer (a washer made up of many thin layers of metal) was used in place of the A1 lock washer. You peeled of layers from the peel washer until the FS was correctly aligned.
With the Phantom, it isn't strictly necessary to align it, as the slots are all around. However, they are usually aligned with the slots at 12, 3, 6, and 9 o'clock, because this is the orientation that leaves the wrench flats in the same position as the A2 FS. However, I recommend that the Phantom be indexed/aligned with 45 degrees more rotation, so that the front notches are at 12, 3, 6, and 9, with the slots at 1:30, 4:30, 7:30, and 10:30. This prevents gas from being directed straight up (in your sight path) or straight down (into the dust), and aligns the front notches properly for optional fence-cutting duty.