Coat the chicken in cornstarch, ensuring it’s fully covered.
Heat the oil in a large skillet over medium-high heat. Working in batches, brown the chicken on all sides, then transfer to the Crock-Pot.
While browning the chicken, whisk together the hoisin sauce, soy sauce, brown sugar, garlic, lemon juice, sesame oil, ginger, and crushed red pepper (if desired).
Once all the chicken is browned and in the Crock-Pot, pour the sauce over the chicken. Stir to coat evenly.
Cover and cook on low for 3 hours, letting the flavors develop and the chicken become tender.
Cook the ramen noodles according to the package directions, drain, and toss them with the chicken and sauce mixture. Garnish with sesame seeds and chopped scallions before serving.