Step 1: Materials
Optionally, if you don't want to tear the paper and you don't have paper of the right size, you can use scissors.
Step 2: Cut the Rectangle
Don't matter about the measurement, it just needs to be oblong.
Step 3: Folding#1
Step 4: Folding#2
Unfold the crease made in previous step and fold as shown in the picture.
Cut or tear the folded line.
Step 5: Folding#3
Step 6: Folding#4
Fold about one third of the rectanglular piece (marked in the picture).
Step 7: Folding#5
Fold one third of the rectangle like in the first picture.
Then, fold the other edge under the first folded edge (like in the second picture).
Then, just fold the upper triangular flap under both rectangular flaps.