  We study four-dimensional Chern-Simons theory on $D \times \mathbb{C}$ (where
$D$ is a disk), which is understood to describe rational solutions of the
Yang-Baxter equation from the work of Costello, Witten and Yamazaki. We find
that the theory is dual to a boundary theory, that is a three-dimensional
analogue of the two-dimensional chiral WZW model. This boundary theory gives
rise to a current algebra that turns out to be an "analytically-continued"
toroidal Lie algebra. In addition, we show how certain bulk correlation
functions of two and three Wilson lines can be captured by boundary correlation
functions of local operators in the three-dimensional WZW model. In particular,
we reproduce the leading and subleading nontrivial contributions to the
rational R-matrix purely from the boundary theory.
