The easiest way to make the collar is by tracing around a large round platter (approximately 18") in the center of the poster board. Trace around a small round plate (approximately 8") centered of that. Cut out. Cut a piece out as shown.
Decorate using glitter, gems, paint and/or markers. Punch a hole in the both sides of the neck edge. Tie a piece of cord in both holes. Slide it around your neck and tie to hold it in place.