3D origami is a simple modular origami with a lot of stylistic freedom making it great for beginners and less experienced folders. I've participated in 3 contests till now and decided to host my own to promote origami and give back to the community. Paper size is A4 format cut into 32 halves, you can make the pieces bigger or smaller, I prefer 1/64 since it uses less paper. Here's instructions on how to fold a unit, the pieces have two gaps and two points allowing them to combine in a few ways:
There are many tutorials online and a whole lot of models, my first was a swan around 6 years ago but have made so many models I don't even remember most. The units are fast and easy to make, you can play around with different colors and stacking methods.
This is how I made the swans at the top (I can make a more detailed tutorial if anyone's interested):
Here's some old stuff I made:
1st place: 2 SBD (1sbd added thanks to 
2nd place: 0.7 SBD
3rd place: 0.4 SBD
Other Participants 0.10 SBD
Since seeing a bunch of posts with 2-5 pieces for the prizes would be boring.
If you need any help just ask :)
Good luck to all the participants!
Edit:
I decided as motivation I'll fold some models and add pics here :)
finished: pokeball(ps. it's way harder than it looks)
here it is next to a crochet stressball I made some time ago:
