Place chicken breasts in the slow cooker.
Add chicken stock, pepperoncini and their juice (I like to put the pepperoncini on top of the chicken), Greek seasoning, garlic salt, and kosher salt.
Cover and cook on low for 6 - 8 hours or high for 3–4 hours.
Shred chicken with two forks, stir into the juices, and serve on buns with mayonnaise and provolone cheese.
Optional step -a quick toast under the broiler keeps the bread from getting soggy and adds a little crunch.