My slowcooker holds about 12 cups, so adjust the recipe as necessary for the size of your slowcooker. First, rinse the peas. My grocery store sells the peas in 16 oz bags, so I use about half a bag and a little. I simply rinse them by pouring them into a strainer and running them under cold water for a few seconds while I shake. Place the rinsed peas on the bottom layer of the slow cooker. Then dice the ham, and place on the peas. Same with the onion, and add the bay leaf. Here's the secret. Shred the celery and carrot. This will result in a smooth and delicious soup. Once shredded, add to the slowcooker. Chop the garlic, add and then add the salt and pepper (as the soup cooks you can always add more to taste. Finally, add the chicken stock, and then fill the rest of the slowcooker with water until you are about 1/2 inch from the top.
My slow cooker has 3 setting, high, low and auto. I cook this soup on high for 3 hours, then switch to low for another 5. Frankly I don't trust my slow cookers auto setting. I mean, really? How does it know how I want my soup cooked? This recipe will make a very thick soup, which is how I like it. If you like a thinner soup, then add less peas. What I do is make the thick soup, and when I reheat it I add water to thin it out.