The body and sleeves are worked back and forth and down top separately, and then join them together by sewing.
A video of how to work popcorn has been uploaded to Instagram: jjloveknitting for your reference.

This pattern includes direction for sizes of 1-2 (2-3) 3-4 (4-5) 5-6 (6-7) 7-8 (8-9) 9-10y

Needle: 3.25/3.75mm needle

Notions: one sewing needle, zip