Prepare the chicken: Pat the chicken thighs dry and place them in the Instant Pot or slow cooker.
Mix basic seasoning: In a small bowl combine 1/2 teaspoon salt, 1/2 teaspoon freshly ground black pepper, 1 teaspoon dried oregano and 1/2 cup water; pour over the chicken and toss to coat.
If using Instant Pot: Close the lid and set to Manual/High for 8 minutes, then perform a quick/manual pressure release; remove chicken to a bowl and reserve juices.
If using slow cooker: Cook on high for 2½ hours, then continue with the glaze step below and cook an additional hour on low.
Make the glaze: In a small saucepan combine the remaining 1/2 cup water, 1/2 cup packed brown sugar, 2 tablespoons low-sodium soy sauce, 2 tablespoons balsamic vinegar and 1 tablespoon cornstarch; heat over medium, stirring, until it boils and begins to thicken.
Combine chicken and glaze: Pour the hot glaze over the cooked chicken (in the slow cooker) or toss the shredded chicken with some reserved Instant Pot juices and glaze; mix thoroughly so chicken is well coated.
Shred the chicken: Transfer chicken to a bowl and shred with two forks, then toss with sauce and let rest a couple minutes to absorb the flavors.
Serve: Serve warm, for example on buns with coleslaw if desired.