i really wanted a small abacus to play with, so i made one out of a matchbox.
beads, toothpicks (or cord/string), matchbox (or any small box, such as boxes for earrings), scissors, an awl/ needle/ tack, glue and tape (optional)
first i used an awl to pierce holes on the sides of the matchbox and stuck the toothpicks with beads on them into the holes. then i cut the tips of the toothpicks off with scissors so they won’t poke out through the sides.
string or cord can be used in place of toothpicks, as long as they are drawn tight and secured in place with knots. in my opinion, the toothpicks have a nicer feel though.
i put clear super glue where the toothpicks meet the box and used tape to secure the box’s edges down and cover the box cover’s striking strip (though that is all optional).