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After making the necessary cuts (which are typically performed using tools like a miter saw for straight and angled cuts, or a jigsaw for more intricate shapes, as suggested by the video's text), carefully position the now-cut baseboard piece against the stair. This step involves test fitting to ensure the baseboard sits snugly against the wall, the stair tread, and the riser, with no visible gaps. Use a white marker to highlight any small areas that require further trimming or sanding for a perfect, custom fit. This iterative process of fitting and refining is crucial for professional accuracy.