An active model for a Ziegler–Natta ethylene polymerization catalyst has been prepared by spin-coating of a MgCl2 solution in ethanol on a flat silicon (100) substrate covered by amorphous silica. The flat model approach facilitates characterization of the catalyst using surface spectroscopy and microscopy techniques. This model catalyst features a Ti/Mg atomic ratio of 0.15 and a primary MgCl2 crystal size of about 15 nm. The flat model is active for ethylene polymerization, producing smooth polymer films. Scanning electron microscopy of these films reveals pillary polymer growth, in the direction perpendicular to the flat support surface.