Take a square of maple, let's say 1-1/2 square by 6" long. Cut a diagonal kerf, but not all the way through, perhaps leaving .1' still attached on one side. Insert the alternate Colored wood of exactly the kerf thickness into the kerf and glue everything up. Rotate the block 180 degrees, repeat the process. When turned down to smaller diameter round, you will have the two interlocking rings. Can be done for more than just 180 degrees. If you want four ovals, repeat 4 times at 90 degrees.
No pics available, but hope this gives you the idea.