This lovely crochet border is known by many names:
• Wave Fan crochet border
• Fan crochet border
• Shell crochet border
• 3D Wave crochet border
There are many tutorials of this on the internet. Below is one of the simplest I could find. YouTube tutorial video by “Crochet by Ellej in English”
You can also read a photo tutorial: 3D Wave Edging from ellej.org
