I use a 3.5 quart slow cooker.  Fill slow cooker about 2/3 full with water and turn to high temperature.  Add:

1/2 cup of lentils or split peas that have been rinsed (or plan ahead and use 1/2 cup of other dried beans that have been washed and then soaked in water over night.  Drain and rinse before putting in the slow cooker.)

1/2 cup of whole grain such as brown rice or barley or bulgur

I turn the heat to low when the water has gotten hot, before it decides to boil over.  I let the beans and grains cook for a couple hours.  Then I add vegetables:

1) clean and dice root vegetables such as parsnips, carrots, turnips, onions or leeks, sweet potatoes - whatever is handy

2) add chopped herbs such as parsley, cilantro, dill

3) any other vegetables you like such as broccoli, cauliflower, frozen mixed vegetables, etc.

I let the beans, rice, and vegetables cook for a couple more hours until everything is soft, then I add 3 vegetable bouillon cubes (I like Rapunzel brand).  After an hour or two more, I have a soup or stew for dinner. I freeze leftovers in 2 cups containers to take to work for lunch.