I recommend printing these in PETG, because it doesn't lose its shape after stretching- but you can use PLA or whatever you like!

This parametric version allows you to choose:

1. Thickness of the disc, 
2. Width of the disc,
3. Number of slots,
4. Depth of the slots,
5. Width of the center hole,
6. and more!

When you make modifications, the rest of the model will adjust itself to keep things functional.

It also includes a parametric magazine type structure to store the discs. The kids I've tested with actually like arranging and storing the discs more than building stuff with them -__-

I was inspired to create this after seeing Vazzed's https://www.printables.com/model/479642-flowersnowflake-building-block, plus I never got to play with these when I was a kid. 

Notes: 

• Disc diameter MUST be >3.5cm if children will be playing with them (default 4). Otherwise they're a choking hazard.
• The slot width parameter is for tightness of fit, Under about 8 years old you want the “kid” setting, which still holds them together but a kid's hands can handle it. Over 8, the adult setting is far more sturdy (and fun imo)
• PETG is a good choice for these, because it stays springy and won't stretch out like PLA, plus kids of all ages will go ape on these and the PLA breaks.
• One wall is ok for adults that will play with these gently, two walls is basically sufficient, four walls is bulletproof and feels solid like a poker chip