Step 1:
I used a paper of about 27x18 centimeters, 1 and a half squares glued together. Prefold in half over both lines

Step 6:
Fold both edges to the centerline, then unfold the model.

Step 5:
Fold both edges to the centerline

Step 2:
Fold both halfs in 3 parts of the same size, this is step 1

Step 4:
Fold the edges to the centerline, then unfold the model.

Step 3:
Use the white bar as help, both parts of the white bar are the same length.

Step 10:
Prefold / make sharper folding lines,
the two outer lines are in the middle of the prefolded lines.

Step 8:
Use the prefolded lines as guidance

Step 9:
Use the prefolded lines as guidance

Step 7:
Fold over the prefolded lines.

Step 16:
Fold over these two lines.
Repeat steps 15 and 16 on the backside.
Use glue if necessary

Step 15:
Fold the edge downwards

Step 12:
The mountain-folds are already prefolded.
Make the same folds on the other side

Step 11:
Fold in half.

Step 14:
Repeat step 12 over these lines.

Step 13:
Repeat step 12 over these lines

Step 17:
Pull the edges upwards on random spots, this will make the edges more visible.