They make a special saw to cut off the bottom of trim. The blade lays
flat on the floor material and the handle is doglegged so that your hand
is off the material. Just lay a scrap piece of the floor material up to
the trim so that you get the proper height of the cut, and saw off the
trim flush with the floor piece.

You don't need a special saw if you use a scrap. It dosen't matter if
the scrap gets gouged. G

Any dovetail, Ryoba, gent's, or small back saw that will fit will
undercut trim.

Barry

If you do a lot of it, Bosch makes an electric version.