I have been working on this for a few years. It is one of those projects that I like to work on for a bit and then leave for a few months. It will probably end up being big enough to turn into a bedspread. I bought a whole load of cotton yarn from Woelle Roedel, which is a fantastic chain of German yarn shops. My parents go over to Germany for family visits so they brought back bags of different colours for me. It is inexpensive 100% cotton yarn which is exactly what I wanted for my colourful granny squares.
When I have made a few squares, I attach them using slip stitch from behind to each other. The more random the colours and combinations, the better! I bought Cotton Universal yarn which was only 2 Euros per 50g ball – a bargain!