In a large slow cooker, combine honey, whole grain Dijon mustard, and water. Stir until well incorporated and smooth.

Gently place the chicken thighs into the slow cooker, ensuring they are fully coated in the honey mustard mixture.

Cover the slow cooker with the lid and set it to low heat. Let the chicken cook for 4 to 4.5 hours.

Mix cornstarch with cold water to create a slurry and stir into the slow cooker, then cover and cook for an additional 20 minutes on low heat.

Shred the chicken in the slow cooker using two forks, mixing it thoroughly with the sauce.

In a mixing bowl, combine chopped red cabbage, olive oil, apple cider vinegar, salt, and pepper. Toss together and refrigerate.

Assemble the sandwiches by filling soft rolls with the shredded chicken mixture and topping with the prepared slaw.