Cut one sock at the heel.

Fill the "foot" part with polyfill to the top.

Grab some thread and wrap around the top to close the sock.

Decide how big the body will be and separate the head from the body with thread.

Hand stitch the buttons onto the body (if smaller kids are making this, use glue instead)

Add pins as eyes and nose (or hand stitch with colored thread; I didn't have black pins so I used thread).

Use the rest of the sock to make the hat. Wrap some thread around the cut end and pull the other end over the head.

Use a full sock as a scarf.

If using polyfill, your snowman might have troubles standing so use 4 pins as "legs". Or here's an idea that occured to me after I've finished my snowmen: right before filling with polyfill, turn the sock wrong side out and wrap some thread around the tip, then turn the sock right side out and proceed as indicated above.

And you're done! Your DIY sock snowman is ready!