Cut out four copies of the following stripes:
Larger versions of this stripe, which you can print out, can be found
here either in PostScript or in
pdf. If you have the stripes, fold upwards
along the dashed lines.
Put two of the paper stripes (as shown in the first step of the following
image - the German word "Schritt" means step) on top of each other in such
a way that the stripes are curved towards the table. Attach the two top
triangles with the help of a paperclip.
Now, fold the stripes to form a double pyramide (as shown in the second
step of the image), by putting the middle triangle of the left stripe
below the middle triangle of the right stripe, and the bottom triangle of
the right stripe below the bottom triangle of the left stripe.
Fix the triangles with another paperclip. Repeat this with the other pair
of stripes.
Put the second double pyramides (as shown in step three of the image) on top of the first. The arrows indicate the next steps in the procedure. Alread after the first of the remaining steps you obtain an octahedron, which is then further stabilized by performing the final steps. The last remaining flap should be plugged into the corresponding slot of the model.