Lay onion slices on the bottom of a large slow cooker.
Lay the chicken thighs on top of the slices of onions.
In a small bowl mix the soy sauce, honey, oyster sauce, ginger, garlic, red pepper flakes, sesame oil and sriracha sauce. Use a whisk and mix well.
Pour all over the chicken in the slow cooker and cook on low for 6-8 Hours.
Remove the chicken from the slow cooker and shred using two forks.
Add back to the slow cooker, with the broccoli, snow peas, carrots, bell peppers, water chestnuts then stir to combine all with the juices in the slow cooker.
Cook on high for another 60 minutes. While the veggies are cooking cook the lo mein noodles per package instructions.
Add to the slow cooker with the other ingredients and stir to combine.
Add chopped green onions and sesame seeds (optional) and serve immediately.
Notes
Once the lo mein has cooled completely store in an airtight container in the refrigerator for up to 4 days.
You can freeze this lo mein recipe, but for best results I would freeze without the noodles and add noodles fresh.
Chicken breasts can be used instead of chicken thighs.