Thanks for the feedback!
daudster: sorry, but its too late for a video. The good news is that there are plenty of good soldering tutorials out there.
This post by Fallon
also has nice pictures that are very close to what I've done myself.
I started with the cable.
My "donor" USB cable was a standard compliant color coded affair. (Red Vcc, Black Ground, Green D+, White D-)
Checking with a multimeter to be safe is a very good idea.
Given the gauge of your typical USB cable wires and the breakout board's holes I suggest you presolder your wires.
Holding the stripped end of your wires with a sufficiently massive pair of pliers will make a nice heat sink to prevent melting the insulation when soldering.
Instead of doing like Fallon and placing the resistor above the breakout board, I soldered one pin on the board, the other on a stripped section of the ground cable "downhill" from the board. If you want to do it like this, make sure that you don't short your resistor with the ground cable. Then cover with shrink wrap.
Lousy ASCII art diagram below:
(Breakout board on the left)
Depending on your exact design, this may not be necessary, but I opted to secure the small gauge wires to the board with hot glue, prior to covering with a larger diameter length of shrink wrap. While this cable's solidity might not be commercial grade, tugging on the cable by mistake would not risk as much damage.
Also a departure from Fallon's post is that I am using a Samsung OEM wall charger that shorts the Data wires in the charger itself, enabling AC mode, so no need to do it on the breakout board. My cable is confirmed working on the computer with both ADB and USB Mass Storage file transfer.
Test as you go to make sure none of your solders introduced unwanted short-circuits. (Fail to do this is and you could very well KILL your precious Nexus S or computer.)
Now, the Fimo part.
This was my first time ever working with Fimo and it turned out to be easy. As you work the material you heat it a little (friction) and it becomes a bit tacky to the touch so I worked on a small sheet of aluminium foil, wax paper might be better yet.
The aluminium plate is used for curing, as its much easier to handle with oven mitts and solid enough for this purpose.
Roll three blocks of Fimo in a sheet about 6-8 mm (¼") thick. With a blade, cut the excess on each side to end up with a properly sized rectangle for the back and bottom of the dock. These leftover bits will serve to support the back as well as the breakout board.
I kept my back flat, you may want to have it curved like the Samsung OEM one. Your choice, I chose flat because its easier to make and to simplify reuse with minimal modification when I'll change phones down the road.
The notch in the bottom for the buttons may be done before or after curing. Before, your fingers, a pen, coffee stirrer sticks or popsicle sticks all work. After, a rounded file or sandpaper.
My first breakout board support was misaligned so I had to break it off. For this reason I suggest you consider doing it in a second curing. This way your test fits are going to be much more accurate.
Most cables aren't rated for high enough temperatures to follow the Fimo in the oven for its curing. That's what lead me to making a support with a notch and using hot glue to finish the job. It's also flexible enough in case your alignment isn't perfect.