forming a mould assembly comprising a central sprue extending along a central axis and an initial mould unit comprising a wax pattern and a seed section connected to the wax pattern, the wax pattern being made of a wax material and the seed section being made of a plastic material, the initial mould unit extending along a unit axis parallel to the central axis, wherein the initial mould unit is rotatable about the unit axis with respect to the central sprue;

providing a seed crystal comprising a primary growth direction;

determining an optimal angular orientation of the initial mould unit about the central axis relative to the central sprue if the primary growth direction of the seed crystal is disposed at a predetermined orientation with respect to the initial mould unit;

rotating the initial mould unit about the unit axis, such that the initial mould unit is disposed in the optimal angular orientation relative to the central sprue;

encasing the initial mould unit in a refractory material after disposing the initial mould unit in the optimal angular orientation relative to the central sprue;

removing the wax material and the plastic material to form a refractory mould unit extending along the unit axis, the refractory mould unit comprising a component mould corresponding to the wax pattern and a seed holder corresponding to the seed section, the component mould comprising a mould wall defining a mould cavity that is disposed in fluid communication with the seed holder and the central sprue, wherein each of the component mould and the seed holder is made of the refractory material, wherein the refractory mould unit is disposed in the optimal angular orientation relative to the central sprue, and wherein, in the optimal angular orientation of the refractory mould unit, the primary growth direction of the seed crystal is angled away from the mould wall, thereby forming a converging disposition with the mould wall in a first region of the mould wall facing the central sprue and a diverging disposition with the mould wall in a second region of the mould wall facing a mould heater;

receiving the seed crystal within the seed holder, such that the primary growth direction of the seed crystal forms the converging disposition with the mould wall in the first region of the mould wall and the diverging disposition with the mould wall in the second region of the mould wall; and

filling, via the central sprue, the mould cavity with molten castable material to form the component as a single crystal structure.