While the arm is curing you can look for a something to mount it to. I used a scrap piece of wood. Now that the putty/weld has completely cured you will need to hold the arm to the wood mount and make a mark where the wire will go. 

Drill a hole big enough for the wire to go through

After the hole is drilled you will need to paint or stain the wood mount. I used red oak wood stain. Make sure to get it down the hole you just drilled. 

While the wood is drying you can mount the skull to the hand. I have made two of these props at this point in time. I made one with the lower jaw intact and one with out the lower jaw. Either way is fine. Put the skull on the hand and find the best spot for it. Move the fingers around and just play with it for a second. Once you have the skull in the right spot, take a marker and the hand from inside the skull, where the cut out circle is. With out moving the arm pull the skull away and put some hot glue just out side of the mark you just made. Let that sit for just a second and then put the skull back on and hold until the hot glue cools. From in side the skulls add more hot glue to the hand and skull.  

Now that the skull is firmly attached to the hand, we now need to secure the fingers. Adjust the fingers to the area that you want them to touch the skull. There is a piece of curled up wire that sticks out of the end of every finger. With a pair of wire cutters, carefully cut that piece off. Use eye protection, sometime the wire will shoot across the room. Now put some hot glue on the end finger bone and attach it to the skull. I then added a drop of glue at each finger bone joint, just in case the tip bone came loose from the skull. This should make it harder for the bones to come off the wire. Do this to all the finger bones.