Here are two downloadble files with many plans for the mats shown below and some so-far untied. They are divided into two groups - those using a Celtic loop pattern (ASTROM)(eg the fourth one from the left on the top row of this first collage)and all others (ROSSING). There is an explanatory READ_ME file in each of the zipped folders. Do try them for yourselves.
Circular Mats Collage
Circular Mats 1 - Using Nils Rossing's ideas
Circular Mats 2 - using Alexander Astrom's ideas