This is the knot style we'll be working with. (Page 33 of Celtic Art: The Methods of Construction.) I highlighted one part of the knot in the diagram, so we can easily see the construction.
To make the knots:
Make to chains of stitches. One or two colors of yarn can be used.
Then I place the other chain of stitches under the loop that I just made.
Now we'll start working over and under, over and under until we've completed the knot.
Now make as many knots as you want. The knots do stretch out a bit. So just know that if you decide to edge the knots, for final item won't be as long. Here are the knots I made for my scarf.
To do a row of edging:
I picked up the knot tail and did a stitch or two on it.
A) Then I picked up and made 4 stitches in the top loop of the knot. (Depending on your knots, you may need fewer or more stitches in the loop. Experiment on a few knots to find out.)
B) Next, I did 3 stitches in the chain that is between knots.
Repeat A and B until you reach the end of the knots.
Do a stitch in the tail of the knot.
Then in the end of the tail, make 4 or 5 stitches (for the corner of your work).
Continue working on the edge of your knots. I did about 3 stitches in each part of the loop on the side.
Continue turning corners and edging until you reach where you started. Pull your stich loops a little tighter so they blend in. Finally, weave in your ends. (I had to use the ends to cover where I started and ended.)