how to cut floor moulding
Slide the compass along the floor over the board's length, keeping the points aligned vertically. With a circular saw set for a 2- to 5-degree bevel, cut alongside the scribe line so the face of the cut will be on the side toward the wall. Trim the beveled edge down to the line with a block plane. When the scribed baseboard is put back on the wall, its top edge should line up with the chalk line snapped in Step 3.
Set a 4-foot level on the floor next to the wall to see if the floor is level. If not, move the level across the floor to find its lowest point. At that point, tack a scrap piece of baseboard to the wall with a nail.