Begin by placing the boneless, skinless chicken thighs in your slow cooker. Make sure they are evenly spaced to allow for proper cooking.
In a mixing bowl, combine the water, salt, pepper, oregano, brown sugar, soy sauce, and balsamic vinegar. Whisk until the brown sugar is dissolved and everything is well incorporated.
Carefully pour the sauce mixture over the chicken thighs in the slow cooker. Make sure the chicken is well coated.
Cover the slow cooker and set it to low. Let the chicken cook for 6-8 hours, or until it is fork-tender and easily shreds.
Once the chicken is cooked, remove the chicken thighs and place them on a cutting board. In a small bowl, mix the cornstarch with a tablespoon of water to create a slurry. Pour this slurry into the remaining sauce in the slow cooker and stir well. Cover and cook on high for an additional 15-20 minutes to thicken the sauce.
Using two forks or a meat shredder, shred the chicken into bite-sized pieces. Return the shredded chicken to the slow cooker and mix well with the thickened sauce.
