Build your mould: Create a square box mould. Make sure it is strong and leak-proof. Prepare the mould: Coat the inside with a release agent to prevent sticking. Create the opening: Place a PVC pipe or round mould in the centre and secure it in position. Mix the concrete: Combine PPC Cement and water to a thick, workable consistency( not runny). Pour and tap: Pour the concrete into the mould and tap the sides to remove air bubbles.