Matrix-based intra prediction (MIP) in current VVC draft applies a two-stage boundary averaging process to generate reduced boundary samples for matrix vector multiplication and prediction upsampling. The two-stage process may cause potential operation dependency and misaligned processes of left and top boundaries. In this contribution, it is proposed to remove the operation dependency in MIP by using a one-stage boundary sample downsamping method. With the proposed method, the dowsampling process is unified for the left and top boundaries. Besides, eight shift and eight add operations are reduced per block.