Summarize:

Place the chickpeas in a strainer and rinse them for 30 to 60 seconds under cold running water. By rinsing the chickpeas now, you clean off any surface debris or dirt clinging to the dried beans. This is also a good chance to pick out any small stones or dark brown chickpeas that accidentally got mixed into the batch. Combine the water, chickpeas, and baking soda in a 2 1/2 qt (2.5 L) slow cooker, stirring slightly to make sure that the baking soda is evenly dispersed and that the chickpeas are all submerged under the water. Note that a pre-soaking is not needed when you cook the chickpeas in a slow cooker. Since the chickpeas will cook so slowly, they do not need to be softened beforehand. The use of baking soda is still recommended, however. Since you are skipping the pre-soaking step here, the sugars do not have the same opportunity to break down as they do with the traditional boiling method. The use of baking soda, which helps break apart gas-inducing sugars, can make the chickpeas a bit easier to digest once finished. If you decide not to use the baking soda, you can add 1 tsp (5 ml) of salt to the water, instead. The salt will not break apart the sugar, but it will add more flavor to the chickpeas, which will absorb the grains of salt as they take in water. As a result, the inside of the chickpeas will be seasoned as well as the outside. Cook on high heat for 4 hours or low heat for 8 to 9 hours. If you want slightly firmer beans, cook them on high for only 2 to 3 hours. Dump the contents of the slow cooker into a strainer to separate the water from the beans. Rinse the beans, still inside the strainer, under running water for 30 to 60 seconds. The water the beans cooked in can contain a lot of dirt and stripped sugars, so it needs to be dumped out. The chickpeas must also be rinsed since some of the debris in the water can end up clinging to the surface of the chickpeas. You can use the chickpeas immediately, add them to a recipe calling for the bean, or save them for another time. Any recipe that calls for boiled chickpeas can use slow cooker chickpeas, though. Note that slow cooked chickpeas tend to be very tender, so you might be better off using them in a recipe that calls for soft, tender chickpeas rather than one requiring firmer beans.
Rinse and drain the chickpeas. Place the ingredients in a small slow cooker. Cover and cook until soft. Drain and rinse well. Serve or use as desired.