This is the most complicated part, because you have to choose the proper materials to make the hand, but it can be also easy if you have the possibility to 3D print the hand (there are many different 3D projects on the web for printing hand parts).
I started making the fingers with cork, to find the proper structure for the movements, then I made it with a branch.
So make three wooden cylinder per finger, two of them with 1 cm over the normal lenght of your phalanx, needed to fit one piece into another.
Then with an angle grinder make the grooves to make the pieces fit together (see the images, you'll understand better).
You'll need some sandpaper to make the pieces curved, so that they can rotate.
Use a drill to make the holes for the hinge, then you have to make other two holes for the fishing wire, vertically, one towards the inside of the hand and one outwards. So when the wires are set at the top of the finger, when you pull the one inwardsthe finger will close, and when you pull the one outwards the finger will open.
The palm was problematic, beacuse I made it initially with wood and the thinner parts always broke. So I decided to make it of steel and I've had no problems.
Cut it and do some protrusions similar to those made for the fingers to fix them to the palm (see the images as a reference). Then use the drill to make the other holes for the fishing wire, the thumb will be tricky because it's not vertical as the ther fingers.
Afer making the hand, you need to make a support for the five servomotors and a support for the Arduino UNO boards. Be sure to choose the right position of the servos, so they don't touch each other while rotating.
The last part consists in connecting the fingers to the servomotors: fix the fishing wires at the top of the finger and make them pass through the holes; then, when the wires are at the bottom of the hand, turn the rotor (manually, without powering it) at his maximum rotation (180°) so that it's in a vertical position, then set the wire that closes the finger to the lowest hole of the rotor, for example making a knot; turn again the rotor at 0° (it's again vertical and the knot made before is at the top) then set the other wire (wich opens the finger) to the lowest hole of the rotor. Follow the last image in this step to understand better.
So, when the motor is at 0° (vertical) the finger is opened and when the rotor is at 180° (vertical again) the finger is closed.