1. Granular rubber is mixed with special bonding material by hand.
2. The mixture is put in a two part (male-female) mold.
3. The mold is cold compressed. (This procedure actually takes place at room temperature.)
Sources:
http://www.answers.com/topic/hockey-puck-1http://www.madehow.com/Volume-6/Hockey-Puck.html
http://www.encyclopedia.com/doc/1G2-2897000054.html