I like extruded clay because of the control you have over size and shape. I’ve been afraid the bangles would be weak. These are not! In fact I was asked if they are made from wood
(Great way to use mud under those veneers too.)
Decide whether you want to extrude the colors you will use or extrude a “base” you will cover.
Tools needed: Extruder, 2 dies which will create extrusions that fit together (like those shown), polymer clay conditioned to be pushed through the dies. An oven-safe armature to shape the bangle to the size you need while it cures.