Well I guess everybody has his own little technik to get more slots ...
I have mine too, which is based on superstition : when I build a rare weap with slots, I keep it in my inv, so when I build other rares it keeps me lucky !
and it works ! I made a 4 slots holy frostration, a 4 slots termi, a 120/120/118/119 2 slots libby, a 3 slots blade of ceres, and more !!
the only problem is that now I have too much weaps in my inv and can't move
indeed, I have tested with high cst skill (without OP bonus), and with just enough skill to cap item stats, and I noticed no difference at all ... but when I went to an OP to make some antiabsorbers, antideflectors, and an antiprotector I had the rare parts, I had 307 cst, I made 1 4 slots antidef on the 5 I built, 1 5 slots antiabsorber on the 10 I built, and the antiprotector was a 3 slots ... So that was just kinda extra luck ? or the best way to slots weapons is to camp a factory ?!