As if looking at the picture wasn't enough, this could be described as simply attaching some velcro with a nut. However, this is my first instructable, so I'm going into detail. :)
Step 1: Get the Hardware.
Any velcro will do, I used stuff for cable management. The nuts are 1/4-20 UNC. I'm assuming you have a tripod and a flashlight. A paper punch and scissors are all the tools you will need.
Step 2: Punch and Cut.
Punch a hole for the threads of the tripod about an 4.5cm from one end. Cut to about 13 cm in length.
Step 3: Assemble.
Screw it together and cover the screw with the smaller piece.
Step 4: Enjoy!
Enjoy a new third hand. It only takes a second to remove and a couple of seconds to put a new flashlight.