I think the placement method of the inserter is always on the right side or in the farthest side if the belt is perpendicular to it.

You can do that to have it placed in the left side : http://image.noelshack.com/fichiers/2016/12/1458763806-capture.png

Or place another belt like this to have ...

I'd like to join you to try some other ways of factorizing

When a friend want you to try out Factorio without explanation :
https://media.giphy.com/media/f1ohcPEHABwWY/giphy.gif

When you have played for some hours and you think about nothing else than Factorio :
http://45.media.tumblr.com/1a7eb36ab53b6c76ff13e65047bfc90d/tumblr_mt60fd4d6a1szo72xo1_500 ...