[Edit - Customizer fixed]
There are several designs for woodworking tools to make chopsticks. This is one - but printed in PLA instead of made in wood. Derived from this Instructable - which is quite cool IMHO.

• https://www.instructables.com/id/Customized-Chopstick-Maker/step5/The-Sled/
• https://www.youtube.com/watch?v=UsKm8szXOq0

So this one is made of three main printed pieces - the template block, the plane block, and a guide for positioning the finished chopstick to plane the prism onto the end.

This object also requires a metal threaded rod (with nuts) to keep it all compressed together. A metal washer needs to be put on the end to act as an end stop to hold the chopstick while you plane it.
The washer needs to be filed so that the plane can move smoothly along the guides. You might want to print the washer 3d model out to use as a template when cutting and filing.

The tool can be customized to make chopsticks of varying length and varying taper.

User chooses:

• length of sticks,
• desired start and end diameters (taper)
• angle of end cut (30, 45, ??)
• amount of tolerance in initial blank for first cut operation (i.e. what size pieces will you start with)

Instructions:

• Assuming a taper from 7mm end to 5mm head (actually adjustable in customizer)

Side1

• planes oversize blank to 7mm thickness
• user rotates blank by 90 and so planes two adjacent sides to get to 7mm

Side2

• puts taper onto two sides
• goes from 7-6mm
• user planes first two adjacent sides of blank

Side3

• puts taper onto the other two sides
• goes from 7mm to 5mm final resulting in equal taper on all sides
• user planes remaining two adjacent sides of blank to final taper

Side4

• v cut to bring into octagonal shape approximating round
  • (can be further smoothed by sanding)
• user planes all four diagonals of the blank

Prism end cut

• end cut does diamond shape at handle end of chopstick
• user attaches guide and inserts chopstick through top plate guide
  • use an offcut of chopstick on the side, through the hole, to jam the chopstick and guide holder in a vice.
• cuts and rotates 4 times to get pointed (octagonal) end

Lengths:

• typically 210mm to 270mm, cooking chopsticks are longer (30-40cm).

chinese - (kuaizi) longer (270) and thicker - do not taper as much as other two.
korean - (jeotgarak, sujeo-with spoon) toughest and heaviest of them all. Medium taper.
Japanese - (hashi-eating, ryoribashi-cooking, saibashi-serving)

• shortest, tapers more than others, taper closer to the end.
• can be ribbed near tip to grab fish.
• 23cm male, 21cm female, 30cm cooking.

"Perfect length" for a specific person is 1.5 times the distance between tip of your extended thumb and forefinger.

To make the plane guide work smoothly - sand the guide surfaces lightly and then apply wax to them. This way the guide will be easy to move and give good results.