You boil and then let settle, then decant.
Same for Worm castings.
If you have issues, then simply allow to soak good in shallow pan outside and keep adding water to keep it fairly moist/wet, slightly submerged.
If you collect nice wetland clays, agriculture soils etc, then you should be able to screen(say 1/8") them with a garden hose into a bucket, allow to settle for a few hours, then decant and allow to dry and then use that without boiling or mineralizing as the soils tend to be already lower in organic matter and high in clays.
These work better over time than most store bought soils.
ADA As is pretty much typical wetland clays that have been enriched with NH4.