Step 1: Supplies!!!
Drill (drill press would probably be even better!)
3/8" drill bit
Adjustable wrench (or wrench for 3/8" nut)
Tripod with 1/4" mounting screw (this is standard size)
Shock mount or microphone clip with standard 5/8"-27 fitting (I think in other countries there are different sizes, this would be US standard fitting)
3/8" to 5/8"-27 adapter $2, here.
3/8" hanger bolt (with one side made to screw into wood, see picture) $2
1/4" Inner diameter threaded insert for wood $2.
3-15 inches of dowel (0.75-1.5") or 2x2, don't buy anything, use scrap!
Note: if you don't have a standard shock mount or microphone clip already, I would experiment. If you have a European fitting, these are 3/8" and you do not need the additional adapter. You should be able to get a plastic microphone clip for about $2-4. Make sure you check thread sizes when you are purchasing/ gathering your materials.
Step 2: Drill, Baby, Drill!
Drill the length of the height of the threaded insert in to the other side of the dowel/ 2x2.
Step 3: Screw Things
Use a penny to drive your threaded insert into the other end.
(The hole I made for the threaded insert was actually too wide so I ended up gluing it in with some gorilla glue, just make sure you keep the threads clean and that it dries completely before you try to put it onto the tripod base.)
Step 4: Adapt!
Ideally the top of the bolt would be flush with the top of the adapter, it is like an 1/8" above here, if you have more than an 1/8th I would put more nuts on or cut the bolt down with a hacksaw.
Step 5: Put Your New Accessory Onto the Tripod Mount
I just tightened the dowel onto the 1/4" mounting post, just like I would tighten a camera onto the tripod.