Preparing paste solder

Hi! I would like to make my own paste solder and I wonder if you can
help me please!

Basically I know is a mixture of powdered solder, flux and a carrier
(according to Orchid archives), but I want to prepare the flux too
(boric+borax?) and “the carrier” is mineral oil? (Vaseline is the
same thing?)

(Where I live paste solder and prepared flux are very expensive,
help me please!)

Isabel