I’ve had similar results by cubing potatoes, boiling them until they’re tender. Drain the water, then throw the potatoes back in the same pan you boiled them in to evaporate any excess water, while shaking them around to slightly break down the outsides of the potatoes. You should be left with like a thin layer of mashed potatoes coating the chunks at this point. Then you can either coat in oil and bake on a sheet tray, or pan fry them in oil.