But it is a difficult concept to get one's head around. Explanations like : "We propose that Saturn’s long-lived polygonal structures correspond to wavemodes caused by the nonlinear equilibration of barotropically unstable zonal jets." require a lot of unpacking (and critical thinking)
As already discussed it is not well understood but there a number of papers that have been published that make some attempt at explaining.
Morales-Juberías, R., Sayanagi, K.M., Simon, A.A., Fletcher, L.N. and Cosentino, R.G., 2015. MEANDERING SHALLOW ATMOSPHERIC JET AS A MODEL OF SATURNʼS NORTH-POLAR HEXAGON. The Astrophysical Journal Letters, 806(1), p.L18.
Rostami, M., Zeitlin, V. and Spiga, A., 2017. On the dynamical nature of Saturn’s North Polar hexagon. Icarus, 297, pp.59-70.
Cosgrove, J.M. and Forbes, L.K., 2017. A δ-plane simulation of anticyclones perturbing circumpolar flows to form a transient north polar hexagon. Monthly Notices of the Royal Astronomical Society, 469(4), pp.4133-4147.
Also this experiment (from the paper posted above by Ian Kennedy) shows how it is possible to create a stable hexagon like structure in a rotating fluid. Although it's not quite the same and Saturn's hexagon should be thought of as more 3D than a single layer.
https://www.youtube.com/watch?v=iheK6JX3rLg
In addition, there has also been seasonal changes in the colour of the Hexagon during the time Cassini was in orbit around Saturn.