Cut out the cat front side up in the middle of the work piece so you can flip it over to carve the pocket for the electronics.
I try to put the tabs on large surfaces that can easily be reached by my belt sander or palm sander. Tabs in crevices can be a nightmare.
Use several coats (3) of primer and after two coats, lightly sand with 220 grit or finer paper to lay the fibers flat and provide a nice glassy surface to receive the chalk board paint.
I did not sand between coats as this paint covers well and lays very flat.
I used an At Tiny 85 microcontroller and the Tiny ISP from Sparkfun to program it just like an Arduino. The code is attached to files. These LED’s have a common ANODE which goes to the positive supply. I used 1 150ohm resistor for each LED. The code increases the analog signal on pins 0 and 1 to bring them HIGH and then LOW again. In this case, when the pin is LOW the LED is lit… see … because of the common anode.
The lipo battery was a great deal – search Amazon for PS3 controller batteries. They come in a nice plastic case.
How does it have an onboard charger? Check out Adafruit.com for lipoly battery chargers. The battery charges when it is plugged in regardless of whether the lights are on. The lights can be on during charging. There is a red led on the charging board, visible through the hot glue – when it is on – it is charging, when it is off, the battery is fully charged.