In large plastic bag, combine flour and salt. Working with 2 or 3 pieces of chicken at a time, shake the chicken in the bag to coat it thoroughly with flour.
In large sauté pan over medium-high heat, warm canola oil. In batches, add chicken to the pan and cook, turning, until lightly browned on all sides, about 4-5 minutes per side total. Using tongs, transfer chicken to the ceramic insert of the slow cooker.
In same sauté pan, place onions and sauté over medium high heat until slightly browned, about 4 minutes. Add wine, scraping bottom of the pan to incorporate browned bits. Add stock and bring to a boil. Cook, stirring frequently, until onion sauce is thickened, about 10 minutes.
Pour onions and sauce over chicken. Add thyme, bay leaves and prunes.
Set cooker to low heat, cover and cook chicken 4 to 5 hours, until very tender and coming off of bones. Remove and discard thyme and bay leaves.