Using the razor, make a relief cut in the paper. Carefully run the razor from the molding corner out to the edge of the paper. Use the molding as a guide.
Press the cut edge tight in the joint between the molding and the wall.
Trim the excess paper flap with a taping knife and razor, ABOVE. Smooth down the whole sheet.
Tip: Hide small cutting errors on darker papers by coloring the wall or the white edge of the paper with a marker that matches the paper. Some pros even color all the paper's edges so seams are not as evident should the paper shrink as it dries.