Toss stewing beef with flour to coat. Shake excess.
In a medium skillet on medium to medium high heat, add 1 Tablespoon of oil. Add ¼ of the beef and brown for about 2 minutes, then stir or flip and brown for 2 more minutes. Add to bottom of the slow cooker, and repeat with the remaining beef in 3 more batches.
Add onion to skillet, and fry for about 2 minutes, stirring a couple of times. Add to slow cooker.
Add potatoes, carrots, celery, beef broth, pickle juice, garlic powder*, onion powder*, beef base*, and pepper to the slow cooker. Make sure all ingredients are covered. If not, arrange to cover or add additional broth if needed.
Cook on low for 8-10 hours, or high for 4-5 hours.
Mix together cornstarch and water. Add cornstarch slurry and peas to the slow cooker and stir. Cover and cook for 5 minutes, or until thickened.
Serve with bread or dumplings
*Or replace garlic powder, onion powder, and beef base with a packet of beef stew seasoning (although adding the beef base as well adds a lovely flavor).**To thaw peas, run under warm water.