Take a square out of a piece of paper with plastic film and use the square paper as a coaster. If you are interested in moving, fold it!
Make a crease along the line.
Make a crease along the dotted line, as shown.
Make a crease along the dotted line.
Flip over and fold both sides inwards along half of the dotted line, as shown.
Fold the other one inward as shown in step 4.
Turn over, fold the four corners inward, fold and flatten.
Coasters are done!!
You can dip the corners with double-sided tape.