I wrote a pattern as I knit the design. Please let me know if you find any errors!

Skills Needed
Double-knitting
Working in-the-round
Following a chart

Supplies
50g each of two contrasting colors of yarn sport-weight yarn
I used a now-discontinued yarn with 196 yards (179.2m) / 50g ball. Look for something with similar yardage per 50g ball, like:
Drops Alpaca
Drops Baby Merino
Nature Spun Sport
3.5mm / US 4 straight and circular knitting needles

Double Knitting Cast-ons:
Knitgrammer Knits
Donielle Showvay The Knitting Coach
Garnstudio DROPS Design

Double Knitting Single Decreases:
Fallingblox Designs