of the chain
a 6mm faceted stone
an enameled pendant
A  openwork pendant
of the  3mm and 5mm rings
a clasp
of the extension chain

To start,  Cut a chain to the size of your choice. For this type of necklace you can start with a length of 50cm.

On the openwork pendant, glue the 6mm cabochon on a wider part to place the stone there.

Once the glue is dry, open a 5mm ring and insert the pendants in the correct order then connect the ring to the chain.

Finally, on one side of the chain, place the clasp with a 3mm ring and on the other side a 3cm piece of extension chain.

Up to you !  Beautiful creations!