My version is not exactly how it is in the movie. It's smaller and the inner circles are supposed to connect. It is also supposed to be ~7cm thick. Mine is ~12cm.
Feel free to interpret the measurements.
My interpretation: 25cm diameter, 7cm thick, 7cm ring diameter.
I was limited in foamcore, so I made mine smaller.
Step 1: Materials
-Pic of Lightdisc to copy (Google images)
-Cardboard or Foamcore
-A compass or something round
-Scissors or rasorblade
-Flour and Water
Step 2: Cut out the circles
Bend both rings inwards. The two open ends will bend together to form a sloped ring.
Step 3: Tape circles together
Step 4: Stuff
Step 5: Optional: Inner connection
I you did it like me, connect the inner rings with a peice of foamcore to fit the gap. Add more newspaper as you go along.
Step 6: Sanding
You probably won`t get a flush edge where the two outer rings meet. So sand the crap out pf them until they are.