Place the baseboard into the miter table for a right-hand cut. The board should be resting on its base, with the face of the board against the near inside wall of the miter.
Position the board so the right-hand edge is just past the right-leaning vertical saw slot as you look at the side of the miter table. The bulk of the baseboard should be to the left of the saw slot. Place the miter saw into the slot and with steady, sure strokes cut down through the baseboard.
Remove the baseboard and smooth off any rough edges with a light rubbing of fine sandpaper.
Place another baseboard into the miter table for a left-hand cut. The board should be resting on its base, with the back of the board against the near inside wall of the miter.
Position the board so the far left-hand edge is just past the saw slot as you look at the side of the miter table. The bulk of the baseboard should be to the right of the saw slot. Cut and sand the baseboard in the same manner as the other.
Fit the two boards together at the corner to ensure the cuts join smoothly before nailing the baseboards to the wall.