Zatarain's, and then I just use it as a side dish or wrap it in a tortilla with shredded cheddar and sour cream. Sooo authentic! But recently I saw (on Pinterest, where else?) a recipe for red beans and rice in the slow cooker and I figured it was time to try making it from scratch. Especially if it was something I could make ahead and let cook all day!
If you want to be authentic, this dish should be made with Andouille (pronounced "an-doo-ee") sausage. However, it packs a spicy kick and can be hard to find - I searched 4 different stores before finding this brand at my local WinCo. If authenticity is not your priority, you can certainly substitute it with a simple smoked sausage. Hillshire Farms seems to be the most popular brand of smoked sausage around here.
Red beans are not the same thing as red kidney beans. They are smaller and have a different flavor. DO NOT cook dried red kidney beans in a slow cooker. They contain a toxin that may not be eliminated if your slow cooker doesn't reach a high enough temperature. For more info, go here. Canned kidney beans are safe for your slow cooker because they are already cooked. Dried red beans (again, not the same as red kidney beans) are safe to cook in your slow cooker. Just wanted to put that out there because many people are misinformed on this subject.
As for Creole seasoning, I use the Tony's brand and find that it's usually pretty cheap (as in under $2). If you'd rather make your own (and therefore control the heat by increasing or reducing the cayenne pepper) here is a popular recipe.
SLOW COOKER RED BEANS AND RICE
slightly adapted from Little Magnolia Kitchen
1 pound dried red beans
6 cups hot or boiling water
1 green bell pepper, seeded and diced
1 medium onion, diced
3 celery stalks, chopped
3 garlic cloves, minced
2 cans (14.5 oz each) chicken broth
1 pound smoked sausage, cut lengthwise and sliced
2 Tbsp. Creole seasoning
hot cooked rice
Rinse and sort beans, removing any rocks or pebbles (yes, I've found some before). Add all ingredients, except rice, to slow cooker and cook on HIGH for 7-8 hours.
This is a rather soupy version of red beans and rice. If you'd like to
thicken it up, scoop up about 1/2 cup of cooked beans and sauce and
puree, then stir it back into the pot. You can also try leaving the
slow cooker uncovered for the last hour of cooking. Serve over rice.