Slow Cooker Corned Beef and Cabbage

carrots, peeled and cut into 3-inch pieces

yellow onion, peeled and quartered

small potatoes, halved

corned beef brisket (about 3 pounds), plus pickling spice packet or 1 tablespoon pickling spice

beers, I prefer ale or lagers

sprigs fresh thyme

head Savoy cabbage, cut into 1½-inch wedges

sour cream

prepared horseradish to taste