A method of forming a cast product (30) by providing a core (52) having a plurality of sections (54) and one or more gaps (55) there-between. The core further includes an insert member (60) spanning the gap (55) between adjacent sections (54). The core (52) is located within a mold (68) and a liquid phase material is introduced into gap (55) between the core sections. The liquid phase material is solidified in the gap so as to form a cast feature of a resulting solid product and the core sections (54) are removed from the solid product (30) such that the insert member (60) remains securely held within the feature (74).