Buy the stencils on Etsy.
Step 1: Materials
- Laser cutter: you could make one for $50, but I had one available.
- Image processing and plotting software: I used Adobe products and AutoCad, but there are certainly other options.
- Face mask for respiratory protection
- Tape: masking tape or painter's tape. The wider the better.
- Stencil material: I used chipboard; transparencies should work as well.
- Spraypaint: I used Krylon indoor/outdoor gloss spraypaint, about $3-4 per can at Walmart (I used Black, Raspberry, Global Blue, and Bright Idea).
Step 2: Choose and Separate an Image
Resize your image:
- Open the image in Photoshop.
- Image > Image Size
- I set "document size" to 800% width/height, at 300 ppi, giving me about 7x9 inches
- Image > Mode > CMYK
- If it asks about Flattening, click "Flatten"
- Normalize using Image > Adjustments > Auto Level, or do it by hand (recommended)
- Open Image > Adjustments > Levels and in the minimum output level box enter 128 (this will, effectively, make the image brighter)
- Select the "Channels" window (next to "Layers", or select from the "Window" toolbar)
- Make only the "Cyan" channel visible
- Select all
- On the "Layers" window, create a new Layer and paste the channel
- You should now see just the Cyan channel in black and white, save this as a jpg
- Do likewise with the three other channels (Magenta, Yellow, and Black)
There is probably a faster way to do the separation, or to do it in Illustrator directly. If you know, share the technique in the comments!