Easy and used in almost every crochet project you’ll ever encounter from sophisticated shawls, sturdy blankets and beyond, the double crochet (US), also known as the treble crochet (UK), is a stitch you'll love having in your crocheting repertoire.
How to double crochet step-by-step (US)
Let's get started. Yarn over, insert your hook in the next stitch.
Over and through. Yarn over once and pull back through that stitch. You should now have 3 loops on your crochet hook.
Keep going. Yarn over once, and pull through those first 2 loops on your hook.
Finish it off. Yarn over and pull through those last 2 loops. You did it! You just worked a US double crochet!