Dave Platt wrote:
There are several.

One way is to laser-print the resist pattern onto a transparency (or
laser-print into paper and photocopy onto a transparency) and then use
the resulting transparency as a photographic mask, exposing a piece of
photosensitized PCB material to UV light through the mask. The
exposed photo-resist is then developed (chemically in many cases) and
the unexposed portion is washed away (or vice versa - depends on the
type of resist) and the board is etched.

Another way is to laser-print the resist pattern (mirrored
left-for-right) on a specialized sort of coated paper. The PC board
material is cleaned thoroughly, the printed paper is placed on the
board toner-side-down and carefully ironed onto the board - the resist
melts and sticks to the clean copper. The board is soaked in water,
and the coating on the paper releases the toner/resist and the paper
washes off of the board. The board is then etched. There are
commercial papers made for this purpose, I've heard of people using
some glossy-surfaced inkjet papers, and some folks even make their own
by brushing a liquid gelatin solution onto smooth paper.

It's also possible to use a flatbed plotter, with a special pen, to
draw resist patterns directly on PC board material.

=================================

I'm familiar with the photosensitized PCB material and UV light method.
But this is hardly an at-home kind of thing. I think I was looking
for the second method you mentioned.