Step 1: Material
You'll just need:
-A bit of a styrofoam tray (or anything that could work as a frame for the LEDs but also that can be pierced, like wood, cardboard, plastics...);
-Some thin wire
And as tools:
Step 2: Assembling the LEDs
Make it in a way that pins with the same polarity are all in the same circle as shown on the circuit scheme. (Notice that in the circuit scheme there are more LEDs than I finally put).
Step 3: Wiring
The simpler way to do it is as you can see in the pictures. Arrange them in circles, and then connect the circles with the same polarity. Then connect the circles to the battery terminals.
*The voltage will be less than required, and so it will be the light output. In case you want more voltage you'll need to hack the batteries system too. For example fitting 3 smaller batteries of 1,5V each. In that case you would need a current limiting resistor, but that's out of the scope of this instructable).
Step 4: Close and Enjoy
If you decide to do it, please try to do it cleaner than mine!! Consider mine as a first attempt to be improved.