Season the chicken breast evenly with sea salt, black pepper, chili powder, and ground cumin.
Heat the olive oil in a medium skillet over medium-high heat until shimmering.
Add the chicken to the skillet and cook for 5 to 7 minutes per side until golden brown and the internal temperature reaches 165 degrees Fahrenheit.
Remove the chicken from the pan and let it rest for 5 minutes before slicing into thin strips.
While the chicken rests, warm the corn tortillas in a dry skillet or over a low open flame until soft and pliable.
In a small bowl, combine the cooked brown rice and black beans, warming them together if necessary.
Assemble the tacos by placing the sliced chicken into the warm tortillas.
Top the tacos with salsa verde, diced red onion, fresh cilantro, and a slice of avocado.
Serve the taco plate immediately with the black beans and rice on the side.