I used 2 strands of 8ply DK yarn with a 5mm hook, but you could use 2 strands of 10ply worsted and a 6mm hook or just use super chunky yarn and the appropriate hook. Crochet over ends as you go where possible to reduce weaving in ends.

Finished size using 2 strands of 8ply DK yarn and a 5mm hook is approximately 9cm wide and 11 cm high without the loop.

The loop allows you to hang it as a decoration.

I later made it with 8ply DK cotton and a 4mm hook and it came out very well.

You may wish to add buttons or beads to your tree.
If you wish you may wish to block or stiffen your tree. Another option is to brush with PVA type glue and sprinkle with glitter for a sparkly look.

Enjoy!
Jane