Step 17: Secondary light sources - Assembling light pipes
Put together a pile of as many LEDs as you'll need, a pile of 2cm-lengths of heat-shrink large enough to go over an LED, and a pile of 2.5cm-lengths of acrylic rod. (You can quite easily cut the rod with a good pair of side-cutters)
Assemble the LED, heat-shrink and acrylic rod together, then using a soldering iron or a heat gun shrink them together. Try to avoid getting the LED too hot, as it can kill them. Repeat until you have a hundred or so of these assemblies. (This is, believe it or not, another step that takes a long time.)
Note: I initially tried melting acrylic rod directly onto the LED. The LED is a different type of plastic so the rod does not 'stick' properly, the acrylic starts to darken when it is heated, and lots of noxious gases are produced. Not recommended.