The materials needed are:
3. plastic bottle
5. hobby knife or blade
6. drill / nail.
First, depending on the shape of your webcam and how you plan to mount it, select the proper plastic bottle. In my case I used a slightly flat plastic bottle as shown. Make sure you can pass the connector end of the webcam cable through the neck of the bottle. You could gently heat the neck over a candle then press it with say a block of wood, this would make the opening oval instead of round, just enough to pass a usb connector through it. I just clamped it with a vice with enough pressure to pass the cable through then released the vice, no need to heat the bottle.
Next, carefully make a hole at the bottom of the bottle into which to attach the tripod screw. Use the bottom of the bottle as it is thicker and will allow of a tight and sturdy fit of the screw and bottle. Make sure the diameter of the whole is just enough for the screw to thread through it and can be tightened all the way so that the bottle is held firmly against the tripod base. This will not be possible if you use the sides of the bottle as it is too thin and will make a flimsy fit. I used a drill bit to drill the hole, but if you don't have a drill you could heat a nail on a candle and then pierce the bottle (hold the nail firmly with a pair of pliers).
Next, I marked out the cross section of the webcam base on the sides of the bottle and cut it out. On one side I cut out a little extra to pass the cable through. First I inserted the cable through the bottle and out through the neck then pushed in the webcam base. I hope the pictures explain it better than I do. Mine can be folded so it does not fall out if tilted downwards. For a snug fit you could try lining the cutout edge of the bottle with a rubber grommet.
Finally, attach the entire assembly to the tripod. Actually it might be a good idea to test how the bottle fits with the tripod before attaching the webcam itself in case some changes need to be made.
Next, this idea could be extended to hold other devices such as directional microphone, flashlight, a smart phone etc. The smart phone on a tripod would be very useful such as when taking time lapse photos or even go a step further and mount two smart phones on a bottle for clicking stereoscopic images / 3D videos.