I centered three cone cups each inside three red cups using scotch tape. Then I used a different red cup to  mix the plaster (2 parts plaster powder to 1 part water). I added a drop of black paint and stirred until it had the consistency of a thick milkshake.  I poured the mixture into the cone cup and added another cone in the center (if it doesn't stay put add some weight inside the cup like a marble or something). The plaster sets fairly quickly but needs 24hrs to cure. Once cured I pulled off the paper cone inside and around the set plaster. I stacked the plaster cones and used hot glue to adhere the wooden star to the top.