For both plasticine and polymer clay
I was tempted to hunt down 1/4" flag lapel pins for dolls online for my Ben Carson teddy bear sculpture, but was reminded of a technique I saw on the Food Network. Turns out to be fast and easy.
A quick word of advice – make the outer layers a little thinner than the rest. I always find that if I make them the same thickness, they don't seem to get compacted equally and wind up fatter. So either you can trim them when you are done pressing them together or start off with a thinner piece.