I place the mask on paper and trace a line around the mask for a pattern.  Make this 3 1/2" to 4” larger oval.  Cut out 2 pieces of fabric and make a pillow by sewing it leaving a 2 to 3" opening to stuff with poly fill.  Leave a tunnel for the prongs on the cage if you are using a tomato cage for the body armature.  Fill with hot glue then slide the prongs or neck dowel inside the pillow.  I melt  a hole on each side of the mask edge to stitch with strong thread to the pillow.  Then seal the edges of the mask to the pillow with hot glue.  The hair glues to the pillow very well and you cannot tell it is not a full head.