I found this really cool video of a celtic knot-style paving circle being dry-laid in 45 seconds. The celtic knot is a very cool design, available from Stonemarket in the UK.
The purpose of dry-laying is to work out how to position the paving stones in the correct arrangement which is especially important in a tricky job like this. It’s much easier to re-lay the paving stones if they haven’t been fixed. Also, with natural stone, there’s significant variation in the colour of the individual stones which makes it a good idea to dry-lay them so that you can align any specific stones based on their slightly different colour hues.