Spread the potatoes across the bottom of a 6-quart slow cooker and sprinkle them with one-third of the seasoning.
Arrange the chicken thighs in one layer over the potatoes and sprinkle on the remaining seasoning.
Lay the lemon rounds over the chicken without squeezing them.
Cover and cook on low until the potatoes are tender and the chicken reaches 175°F, 4 to 4 1/2 hours.
Discard the lemon rounds and transfer the chicken and potatoes to a platter.
Spoon the lemony pot juices over the chicken, leaving excess fat behind.