So you could just dissolve your meth/e mixure in water, bring PH up so both became freebase, oil will be floating ontop while crystals will be suspended in the water
If by 'E' you mean Ephedrine; sorry it wont work as you describe. Freebase ephedrine is soluble in water, so no crystals will be 'suspended' in the water.
One more way i was thinking of is if you distill for a post reaction workup because E distills very very poorly, steam distillation is needed to move E over where the meth FB will move over without steam
You're on a better track there...
https://www.thevespiary.org/rhodium/Rhodium/chemistry/meth.ephedrine.steam.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/meth.ephedrine.steam.html)
" A separation of ephedrine from the amphetamines seems possible if a steam distillation as mild as possible is used to isolate the amphetamines. Then a forced steam distillation can be used to separately collect the ephedrine."