I am not sure this picture will show up well enough to see the serving clearly, but I will include it anyway and try to explain how I triple serve a string.
I first serve the string normally. I use 80-pound SUFIX Performance braided fishing line rather than serving material because it is stronger, slicker on the fingers, and takes abrasion much better.
Then I place an arrow on the string and start a second layer of string immediately below where the nock fits on the string. I wrap that layer maybe a half inch longer than layer one so the end smooths out nicely.
Then I serve the same area a third time, also taking this layer about a half inch below where layer two ends so the end smooths out nicely.
That's it. Pretty simple. The are where the nock fits on the string has one layer of serving, the area where my fingers contact the string has three layers of serving.
As you can see, I shoot three fingers under (although I place the arrow in the same position as someone who shoots with one finger over the arrow----if they nock with the middle finger on the eye tooth).
If you shoot with one finger over, you would also need to serve two more layers above the nock.