Ok, I watched part of it. Here are my criticisms so far.
1. I think you might have meant 30 CENTIMETERS. 30mm seems kind of small. I'd have just said "A ruler or straight edge".
2. I'd have also said DF4L's full name.
3. Lighting could be better.
4. Maybe have everything set up in a well lit room on a table.
5. You might also list some of the other methods available. Like hot glue, super glue, elmers glue, or rubber cement, and the X-acto knife or pen and ruler methods. I personally freehand it with the X-acto knife. I also use elmers glue.
Disclaimer: I have no idea what I'm talking about.