Step 1:
The backside of this paper is completely white. Turn the paper.

Step 6:
Pull the end at the bottom of the arrow upwards by making a valley-fold over the green line.

Step 5:
Unfold the folds of step 4

Step 2:
Prefold over these 4 lines.

Step 4:
Make a valley-fold over these 2 lines. Make these folds over the 2 upper layers of paper.

Step 3:
First, make a valley-fold over the 2 lines at the bottom-right. Then, make a mountain-fold over the 2 lines in the middle. And make a valley-fold over the 2 lines at the top left.

Step 10:
The arrow shows the flap of step 9, press it flat. Make sure that the 2 green lines get in an angle of 90 degrees

Step 8:
Repeat step 4 to 7 on the backside of the model.

Step 9:
Pull the flap at the bottom of the arrow upwards,  in the direction of this arrow.

Step 7:
Press the edges downwards from above, see arrows. You don't have to make new folding lines to do this.

Step 16:
Make 6 of these pieces for one complete modular ball.

Step 15:
Turn the model.

Step 12:
Push the place indicated by the arrow flat from above. Make sure that the 2 green lines get in an angle of 90 degrees

Step 11:
Insert a finger in the opening of the flap at the bottom of the large arrow, so this flap becomes flat to. Then pull this flap to the left, in the direction of the large arrow. Pull/push the corner at the small arrow in the middle a bit upwards, to the place indicated by the upper arrow.

Step 14:
Press the flap flat from above. Make sure this flap gets in an angle of 90 degrees too.

Step 13:
Pull this flap upwards too

Step 21:
And make one more valley-fold over this line.

Step 19:
Repeat step 18 over this line

Step 20:
Repeat step 18 over this line.

Step 18:
Connect the 2 flaps by making a valley-fold over the short green line at the left of the arrow. Make this fold over both flaps in once.

Step 17:
Press the 2 flaps indicated by the arrows against each other.

Step 22:
Pull the 2 flaps indicated by the arrows outwards

Step 25:
Repeat step 18 to 21 on these 4 sets of flaps.

Step 26:
Turn the model

Step 24:
Repeat step 18 to 21 with the flaps at the 2 large arrows and also with the flaps at the 2 small arrows.

Step 23:
Repeat step 18 to 21 with these 2 flaps

Step 27:
Repeat step 25 with this final piece