Here’s a simple Celtic knot you can make using only paper and scissors.
Download and print 1-16-15 2×3 knot template. There are two templates in the file. They are mirror images of each other.
Cut out the two loops (cut out the doughnut holes in the middle, too).
Cut open the loops along the dotted line.
The lines across the loops indicate where another loop crosses over it.
Arrange the two loops to look like this: