I'm going to show you how to do a sonobe modular ball, with a little twist to it. If you aren't aware what that is click this link to check it out.

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Step 1: Materials

All you need is 12 square sheets of paper. Make sure it's double sided so you can get the design correctly.

Step 2: The Units

Start with the white side up and fold in half horizontally. Crease well and unfold.
Fold both the top and bottom halves to meet in the middle. Crease well and unfold.
Make a small diagonal fold on the top left corner and the bottom right corner. Crease well
Flip paper over.

Step 3:

After flipping your paper over make two diagonal folds as shown. Crease well.
Flip over again and close.
Make two horizontal fold on the top and bottom flaps as shown. Make sure the edges on the bottom and the edges on the top match.

Step 4:

Open up top flap and fold bottom left corner to meet the middle. Then fold in the upper right corner inside the bottom flap.

Step 5:

Make two horizontal fold as shown. Crease well and turn paper over.
Make two vertical folds as shown and unfold.
Finally fold in half as shown and unfold.
You are now done with one unit make 11 more.

Step 6: Assembly

Now that you have your 12 units its time to put them all together.
Take two units. See how they fit together? Insert one small corner inside this small slot.
Assemble four together for your base as shown.