Cut the celery, onion, and carrots into large chunks. Place veggies at the bottom of the slow cooker. Sprinkle veggies with greek seasoning.
Layer the bone-in chicken on top of the veggies, sprinkling skin with salt and pepper
Cook on low for 6-8 hours
Making Chicken Broth
Using a spider or large slotted spoon, carefully remove all the chicken onto a plate to cool.
Scoop the boiled veggies into a blender and blend well so that no pieces exist
Pour the blended veggie broth into a large stock pot over medium heat to boil
Once it is boiling, lower the heat to simmer and begin making the dumplings
Dumplings
Measure flour and poultry seasoning into a mixing bowl or stand mixer, whisk them together.
Add shortening and bacon drippings, mix on low till flour resembles course sand.
Add milk and stir on low until dough comes together, feeling like playdough.
Roll dough onto floured surface to desired depth and cut into preferred dumpling shape. Using a spatula, transfer dumplings into simmering chicken broth. Give them a stir to avoid them sticking together
Cover and simmer the dumplings for 20 minutes.
Once dumplings have cooked and are puffed up, de-bone chicken and drop chicken into the pot.
Give the pot a stir, cover, and let chicken warm back up. Serve chicken and dumplings warm.