Draw a grid on the back of the material of at least 3 columns; there' s no hard and fast rule, you can do as many as you like.
You should draw squares (here they are 1cm by 1cm) but they can be 2 or 2.5 com for a larger plait.
You will need to draw a line for every other square, in one direction and then the other...
You will need a needle and a strong thread.
Sew the corners of each of the sides of the squares depending on the direction.
The do a tight knot.
With patience, you will see your plaits forming in your material.