Wow very nice! Is that card stock you're using there? Your cut circles look damn near perfect to me! Did you use regular old scissors?
As an aside, having never used a slide rule before and not being the most mathematically adept person out there, I was up until 2am scoping out the web for a user friendly guide on slide rule operations. I came across
this site at UC San Diego where a professor holds a seminar on slide rule operations. How about that! He has a 13 MB .pdf file of his PowerPoint presentation
here Good stuff for beginners.