Step 1:
Tape or glue four a4-size papers together.
Then, mountain-fold over these 2 lines.

Done,  Let's dance!

Step 8:
Turn the model.

Step 6:
Make an inside reverse fold on both edges.

Step 11:
This is the inside of the model.

Step 10:
Push/fold the edge inwards on four places, see arrows.

Step 9:
Make an inside reverse fold on both edges.

Step 5:
Mountain-fold over these eight lines.

Step 7:
Press this edge flat by making a valley-fold over the line on the right and a mountain-fold over the line on the left.
Do the same on the other side.

Step 3:
Mountain-fold over this line.

Step 2:
Valley-fold over these two lines.

Step 4:
Mountain-fold over these four lines.