Rinse beans thoroughly using a colander or strainer, swishing to remove any loose dirt.  Remove any stones or pebbles.  Add beans, water, garlic, and onion to the crock pot.  Stir and cook on high 3-4 hours or high ~6 hours.  About 30 minutes before finishing, stir in cumin and salt.  At the end of cooking, sample the beans to make sure they are tender.  Exact cook time will depend on the heat of your crock pot.  Strain beans, reserving liquid.  Remove onions if desired.  Stir 1/2 cup of reserved liquid back into the beans.

To Freeze:  Portion the beans out into desired serving sizes (I like to do some larger bags where I serve the beans as a side dish, and some smaller for when I'm just adding them to an existing recipe).  Spread the beans flat in the bag and freeze.  For more info, see my freezer tips page.