Steak Soup

First of all, not sure why this is called Steak Soup, but whatever.
I am really bad at letting the kids cook with me. I feel like we have very limited usable counter space and I like to just do it myself, BUT I am really working on that because I know it's good for them to learn their way around the kitchen and they really enjoy cooking. It's getting easier to let them help as they get older too.
We do "helper weeks" at our house because it's the best way for me to keep track of who gets to be my kitchen helper. This week Peter is my helper so I let him look through some cookbooks to choose something to make and this soup from Fix it and Forget it was his choice-

2 lbs ground chuck, drained and browned
5 cups of water (I used beef broth and eliminated the boullion below)
1 lg onion, chopped
4 ribs celery, chopped
3 carrots, sliced
2 14 1/2 oz can diced tomatoes
10 oz bag frozen mixed veggies
5 Tbsp beef boullion granules (or 5 cubes)
1/2 tsp pepper
1/2 cup melted butter
1/2 cup flour
2 tsp salt

1. Combine chuck, water, onion, celery, carrots, tomatoes, mixed veggies, beef granules, and pepper in slow cooker.
2. Cover. Cook on low 8-10 hours or High 4-6 hours.
3. One hour before serving, turn to High. Make a paste of melted butter and flour. Stir until smooth. Pour into slow cooker and stir until well blended. Add salt.
4. Cover. Continue cooking on High until thickened.

I just realized that I forgot to do step #3- oops. Oh well, ours was actually healthier then!