I laser align frequently to hear various amounts/types of toe.
The first thing I do is find the ceter of the room.. not as easy as it sounds if you want to get it to within a millimeter. 'Right about here' does't cut it. Then I have to line up the primary listening position into that spot... and center that to the room... using a dummy head/stick/etc. Once that's done you have a place to point lasers.
If your speakers are perfect boxes, you are in good shape since you could then secure lasers to the inside and outside edges... but even then, how would you know how far away each speaker was from the focusing spot? You could get the angles right but not the distance.
Since you have now found only 1 spot in your room, you'll still have to find a way to put the speakers in the same plane... I do this by finding a 2nd center spot in the room, between the speakers. I then measure out from the center the same distance from each side... never use the walls... they lie!
If you were to then attach lasers to the edges of a perfect box-shaped speaker, very carefully so that they are all positioned exactly the same, THEN you could achieve a really good alignment.
I do all of this with 1 measuring laser.. I use a combination of speaker placement methods and some of my own to achieve what I like.. I should really write it all down sometime. It's fairly predictable and sounds great which I like.
-C