You need to know how to
“knit in the round” on dpns, I-cord, and long tail cast on.

Use small amounts (20 yds) for shells and (5 yds) for filling of two different weights of yarns from worsted weight to fingering weight.

And knit using needles 2-3 times smaller to get a dense fabric.

Macaroons are knitted in three parts:
Two double-layered shells and an I-cord ring filling,
then the I-cord ring filling is sewn between the lightly stuffed shells.

The shells can be started using either “Emily Ocker Cast On” or (no slipknot start) Longtail cast on.
There are instructions for both ways with lots of photos.

There are instructions with photos for Kitchener Stitching the ends of an I-cord into a ring. But you can sew the bond off ends together too, it’ll just won’t be as smooth.