Step 3: Measuring the armor and cutting
I didn't make a pattern, just laid out the pieces and marked where to cut with chalk. Not at all tricky.
You might use large, sharp sheers if you have them. Whatever is handy and very sharp. Probably not going to cut it in one go. I have no idea what armorers use to cut this stuff. Probably big sheers or some industrial cutting machine.
I used a rotary cutter and sheers.