A method of supporting a hydrocarbon synthesis catalyst material comprising a catalytically active metal and a carrier material on a substrate comprising the steps of: (a) applying the catalyst material to the substrate; and (b) heating the catalyst material to form a catalyst material layer fixed to the substrate, characterised in that—the catalyst carrier is a porous inorganic refractory oxide or precursor therefor; the catalyst material applied in step (a) comprises 60 to 90 weight % solvent calculated on the total weight of the catalyst material layer; when the catalyst material is subjected to the heating step (b) it comprises at most 10 weight % of solvent, calculated on the total weight of the catalyst material layer; in heating step (b) the catalyst material is heated to a temperature in the range between 250° C. and 800° C.; cracks having sub-millimetre widths are uniformly formed in the layer; after step (b) the catalyst material layer has a thickness of 5-200 microns. The control of cracking of the catalyst material on the substrate, especially the presence of cracks at regular distances such that there is no continuous catalyst layer on the substrate surface, reduces any stress build-up.