Honestly, this is one of the easiest builds ever. Most of the effort went into finding the perfect laser safety window material. I settled on P5P21 from LaserSafety.com. This is because of a few reasons- 

• It's polycarbonate instead of the regular acrylic so it's shatter resistant and I can use these for grinding and general safety as well
• The laser safety specs are kinda crazy! Look into the project details above for more on this.

I ordered a 12x8" sheet ofP5P21. 

Cut it into 51 mm circles using a bandsaw and deburred the edges. Then I replaced the glasses in stock steampunk laser safety glasses with these. That's all there is to it!!