First, draw the shape you want on the paper. I drew something big to make it easier to cut out, but you can make it whatever size you want.
Color it, cut it out, and tape it. Leave plenty of tape for sticking to the doll's face.
Attach it to the face and you're done! You can adapt this tutorial to basically anything - this is how I made Cora's hearing aid.
What do you want to see next week?