tl;dr is paint poured onto the middle of a structure or canvas and it runs down. It's kind of similar to the [rainbow cake] process.
Featured on the [ColourLovers.com] entry:
[Holton Rower] pours paint over a custom "canvas" of boxes and panels, one color on top of the other. The result is somewhat psychedelic but this kinetic-process created work is anything but one-dimensional.