Place the chicken cubes in the slow cooker. Add 3 tablespoons of the chili powder, stir to combine. Add the rest of the ingredients, except for the beer and toppings.
Stir everything together, cover, and cook on LOW for 6 to 8 hours.
Just before serving, stir in the remaining 1 to 2 teaspoons of chili powder and beer, if using, season with more salt and pepper, if desired.
Divide the chili among warm bowls. Serve with your choice of toppings.