Place the tomato sauce, tomato paste, soy sauce, vinegar, honey, scallions, garlic, ginger and red chili flakes in the bowl of a slow cooker and stir to combine. Add the chicken and cover with the sauce. Cook on low for 6 hours or high for 2 hours.
Remove the chicken and place it on a cutting board. Shred the meat with two forks.
Mix the cornstarch and water in a small bowl and add the mixture to the sauce in the rice cooker. Cook on high for 5-10 minutes until the sauce thickens. Reserve about ¼ cup of the sauce in a bowl to drizzle on top of the nachos. Add the shredded chicken to the remaining sauce in the slow cooker.
To make the pickled cucumbers, mix the vinegar and honey together in a shallow bowl. Add the cucumber slices and let sit for 10-15 minutes.
To assemble the nachos, spread the tortilla chips out on a baking sheet. Top them with the cheese and about half of the pulled chicken (save the remaining chicken for sandwiches another day). Turn the broiler on and place the tray under the broiler for 1-2 minutes until the cheese is melted.
Remove the baking sheet from the oven and top the nachos with the pickled cucumbers, diced bell pepper, sesame seeds, scallions, cilantro and the reserved sauce, as desired.