Materials: (feel free to make substitutions)
card stock
glue
scissors
straws
string
bead (or hot glue)
Step 1:
Have the child trace their hand onto a piece of card stock or thin cardboard. Needs to be stiff but still easy to bend.
Step 2:
Cut out the hand.
Step 3:
Cut straws into 19 pieces. 14 small pieces for the bones in the fingers and 5 longer ones for the bones in the hand.
Step 4:
Glue the pieces of straw onto the hand. See the picture for help. Talk about the placement and how they are representing the bones in the hand. Make sure and allow the glue to dry completely before continuing.
Step 5:
Run a separate piece of string through each set of straws representing each finger. make sure and leave extra at the bottom to pull. Either tie a bead to the string at the top of each finger or hot glue the string to the tip of each finger to make sure the string stays in place and is able to be pulled. 
Step 6: Time to experiment. Discuss how the parts of the model represent the human hand. Talk about what other changes could be made to improve on the mod