I'd noticed a while back that the sailor's breastplate or carrick mat is a good way to start an ocean plat, and realized that any turk's-head mat could have a prolong-knot tail added to it if you lead the ends out instead of "completing" it.
Here's an example of what that can lead to:
http://www.golden-knots.com/composite_knots.htmlInterestingly, it was not possible to complete it in a single line until I gave up on making it symmetrical.
Loren