This method comprises following steps: - positioning a separation tool (80) in the inner volume (22) of a container (12) for delimiting at least one first region (84) and at least one second region (86) separate from the first region (84) in the inner volume (22)； - interposing a flexible material layer (82) between the separation tool (80) and the container (12)； - deforming the flexible material layer (82) by a first material precursor and by a second material precursor upon filling the first (84) and the second region (86)； - withdrawing the flexible material layer (82) out of the inner volume (22) after solidification of the first material precursor and of the second material precursor.
