I make free-hand drawings of Celtic Knot work (I specify “free-hand” because people always ask where the stencil is). I saw this idea online a couple of years ago. I started drawing basic squares but my designs have gotten more intricate over the years. If you don't get it the first time keep trying! It takes awhile to perfect the steps involved, but eventually you'll be drawing them in your sleep.

Step 1: The Border

If it's your first time, use a grid. The bigger the grid, the easier it will be (1 in x 1 in shlould be good). Put the grid under your paper and follow the grid to make a border. Making a rectangle would be the easiest, but when doing something more complicated, the more symetrical the design the better it will look.

Step 2: Complete the Pattern

To complete the pattern, start with corners and work your way towards the center. You're basically drawing two kinds of squares: squares inside grid squares or squares around four corners of grid squares. If you want to get fancy, you can add turning points, which is just connecting two squares. The more turning points you have, the more interesting it will be (again, try to keep it symmetrical).

Step 3: Over Under

Over under over under over under over under over under. Do that about 500 times and you should end up with one giant knot. Take your time when doing this. Most likely, the first thing someone will do when they see this is follow the line, and if it doesn't go over under over under they will make sure to point it out to you.