It may come as no surprise that piecing together the hand is one of the most intricate aspects of the project. For this reason, it's a good thing to save it until the end so that you are more comfortable with lining up your drill marks.
Given the number, size, and similarity of the bones, it's a good idea to take special care lining everything out before drilling.
Here are all of the bones laid out in advance. The phalanges are remarkably similar across different digits, so make sure you identify the small numeric markings that are cast into them. It follows a sequential order so that metacarpal of D2 is one number lower than the proximal phalanx of D2, which is one number lower...and on and on.
When you have the phalanges laid out in order, simplify the situation by binding them together with heat shrink tubing. You'll quickly have far fewer pieces to worry about, which on this project is a good thing.
Pictured below are two of the bones awaiting application of the heat gun, and all the phalanges joined together.
Glue together the metacarpals
The bones of the hand are so specifically aligned that I recommend gluing them together initially to make sure that you have them oriented correctly. The subtle variations in surfaces fit together remarkably well. It's a testament to the quality of this reasonably priced model that these things fit so perfectly.
It's easier to orient the metatarsals and work backwards from there, so use some superglue to fix metatarsals 2 through 5.
Fix the carpal bones to the metatarsals
The carpal bones are particularly challenging because their shapes are non-distinct. Take your time.
Begin with the distal bones (moving left to right): trapezoid, capitate, hamate.
Then move to the next row of carpal bones (left to right): scaphoid, lunate, triquetrum, pisiform
Take care with this step as keeping the correct identity and position of the bones can become mildly disorienting. When they are positioned well, they will fit like a key in a lock. If you are in doubt, it probably isn't quite right yet.
Not pictured here is the trapezium bone which will join to the thumb, but it's placement will be shown in the final finished shot.
Drill holes and bind it together
Here the entry point for each drill hole is marked out along the back of the hand. Similar marks are made along the front and provide a way to visualize that path that the cords should take so that the joint surfaces can be bound together as securely as possible.
In the second picture you can see the bungee cords in place, including for the trapezium. You can also see that in the final product, I switched the MCP joints to a soft joint with a bungee cord as opposed to the more rigid heat shrink tubing. This was accomplished by two holes at right angles to each other on each side of the joint.
With the hand in place, it becomes possible to move on to the final stage of this project: the elbow and wrist.
By Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body, Gray's Anatomy, Plates 219 and 220, Public Domain