Another thing to mention about cutting, is the idea of always cutting away and not towards you. There are reasons for this that involve the ways our bodies work as well as safety. I will position squares so I can do two sides at a time, but otherwise am always cutting away.
So, since I didn't clarify before, no matter what direction the fabric is, and whether I use two rulers or one, I am always cutting away from myself with my rotary cutter in my right hand. My left holds down the ruler, and I cut along the right leading edge of the ruler
I went for decades with no cutting accidents -- haven't turned 10 years safe yet but then I had a run where I cut myself badly like 3 years in a row. I am a little sloppy about always covering my blade, but one of my Tuesday group ladies is big on preventing accidents that way. I can say recently I was very happy when I dropped my cutter on my bare foot but the blade was safely covered.