Add 3 teaspoons of oil to the bottom of a cast iron skillet. Heat the skillet up over medium high heat.
Season the beef with salt, then add to the skillet. Cook on each side until brown, should take about 5-10 minutes depending on the size of the pieces.
Remove from the skillet from the heat. Take the beef out of the skillet. Add about ½ cup of water. Using a metal spatula scrape the bottom of the pan to get off anything that stuck. Add that liquid to a slow cooker.
Add an additional 5 ½ cups of water to the slow cooker.
Add in bay leaves, Worcestershire sauce, dried mushroom powder, and salt to taste. Taste the liquid and add more seasonings if you feel like it needs it.
Cut the onions, potatoes, and carrots into large chunks and add to the slow cooker. Then add in the browned meat.
Set the slow cooker to low and cook for 6-8 hours.
See notes for ways to thicken your beef stew.