It is very easy to do and can be a great deal of fun. I decided it might provide some light relief while I am knitting intricate lace. I used a square with the corners cut off so that it is an 8 sided figure with a circle cut in the middle and a cut into each one of the sides. I threaded seven different colours of yarn, embroidery cotton, down through the centre hole and seat one colour in each of the cuts, leaving the eighth one open. Knot the colours together underneath and tie a weight onto them. I used metal washers. The skeins lie over the top and hang down the sides anchored in the cuts.
Work in a clock-wise direction. Take the 3rd colour thread to the open space. Repeat with all the strands and the cord begins to form. It looks like this.
Move the weight periodically as the cord grows and soon there is a growing length of cord. It is simple and fun. I have used them for draw stings, hat ties, bag handles and cardigan ties. The thicker the yarn is, the faster it grows and the thicker the cord is. I have used embroidery cotton here because I am making a coaster and I want it to be washable.
This is what the start of the coaster looks like. I am stitching the cord together in the round.
It is great fun. It is also a project that is easy for children to learn quickly and enjoy.