Using the Millot-Sire interpretation of the half-Laplacian on as the Dirichlet-to-Neumann operator for the Laplace equation on the ball , we devise a classical approach to the heat flow for half-harmonic maps from to a closed target manifold , recently studied by Wettstein, and for arbitrary finite-energy data we obtain a result fully analogous to the classical results for the harmonic map heat flow of surfaces and in similar generality. When is a smoothly embedded, oriented closed curve the half-harmonic map heat flow may be viewed as an alternative gradient flow for the Plateau problem of disc-type minimal surfaces.