Step 1:
Tin foil is taped to one side of this black paper.
Fold in half

Step 6:
Press these spots flat, see arrows.

Step 5:
Make the same folds on the other side.

Step 2:
Valley-fold.

Step 4:
Fold the edges to the centerline, then fold the model in half

Step 3:
Prefold in half.

Step 10:
Mountain-fold over these two lines, make the same folds on the other side (=valley-folds).

Step 8:
Now the model looks like this.

Step 9:
Hold the model at the spot indicated by the large dot. Then squash-fold the part on the right.

Step 7:
Press both lines towards each other, make the same folds on the other side.

Step 16:
Press / fold these two spots inwards.

Step 15:
Make the same fold on the other side (=valley-fold).

Step 12:
Fold the edge inwards, do the same on the backside.

Step 11:
Insert the end into the opening, see arrow. Tape or glue both parts together (if neccessary)

Step 14:
Sink fold the part between the blue lines. And fold the edge indicated by the arrow to the left, do the same with the edge on the backside.

Step 13:
Lay one edge over the other