See if you can find a copy of the Jinks McGrath "The RIngs Book."
Pages 102, 103 show the clearest illustration of one way to set from
the back... There are other methods, including tabs, rivets, and
screws -- but this one is nic e, neat, clean and simple. It only
requires a soft metal square wire -- fine silver or high karat gold,
about 22 gauge, and an onglette or pointed graver . Done correctly you
can set the most delicate stones using this technique.
Basically you cut the seat in reverse to fit your stone up from the
inside/back of the ring. Then cut your square wire to size and form
a "bezel ," making sure that it is a tight fit when shoved up against
the stone from the back o f the ring. I cut a little bevel on the
side that will be against the stone to act as a seat. When that is
done and everything fits well, put in your stone from the back, then
your collar or bezel up snug against the stone and secur e it by
carefully pushing up "threads" of metal from the inside wall of ring
itse lf to hold this retaining ring/collar/bezel (or whatever you want
to call it) i n place. The only danger you will encounter is if you
slip while cutting the threads or grains from the inside wall. Make
sure your graver is sharp, supp ort the ring so it cannot move while
you are pushing them up, and take your time...
The Blaine Lewis tapes do not cover this method, and not having taken
any of his live workshops I can't tell you if he teaches it in them.
Might email him & ask?