Ignore all these *****in jerkoffs who think desomorphine is the same thing as krokodil. Just figure out solubilities of desomorphine, phosphorous acid, hydroiodic acid, and whatever else. Then find a the right solvent to extract the good stuff
Technically this is not possible. BTH is mostly 6-MAM instead of actual heroin.
You can make "cheese" heroin with OTC paracetamol hydrochloride. That's pretty close.