I think I can help.
Start with making 3 conical collets. Each of the stones must fit
inside with 1 mm of metal protruding above the girdle. The thickness
of the metal depends on stone size. I mm for 6mm stone is fine.
Take center collet and file flat areas on the side approximately
half of the thickness. The flats must be opposite each other. Side
collets only get these flats on one side only. Solder collets
together. The bottoms must form an arch fitting the shank. You can
file it precisely after soldering, just have extra height.
Important to keep collets aligned. The centerline of collets must
form a straight line.
Next is under-bezel, which is metal strip fitting the bottom of the
head ( three collets soldered).
In the picture it is made of yellow gold.
Take triangular file and file notches in the bottom of each collet.
You also have to remove metal from between the collets on the
bottom. This is done with jeweller’s saw. On the picture each collet
has 4 notches. 2 aligned with the shank, and 2 perpendicular to the
shank. If we look at the first picture, we see 5 notches total. 2
formed between collets, and 3 notches in the center of each collet.
Notches should as deep as 1/3 of the height of the collet (
personally I like a bit higher ). File channels with triangular file
running from the top of the notch to the top of the collet. 1/2
thickness of metal. You should have now what you call inverted "V"
only with inside still filled with metal.
Give them good shape and pre-polish ( only areas inside notches ).
Solder head ( 3 collets ) to the under-bezel at this point and
solder in the shank. This would give you means to hold the whole
for the next step.
Holding ring in the ring clamp, cut out metal from inside the
"inverted V" with jeweller saw. You must make sure the prongs
resulting from this are strong. Take you time with this.
After sawing is done, smooth it with files and you should have it.
When setting stones, the areas between settings is split with fine
jeweller saw ( #8/0 ) and turn prong over like usual.