Heat olive oil in a large skillet over medium-high heat.
Add beef tips and brown on all sides, about 5-7 minutes. Remove beef from skillet and set aside.
In the same skillet, add diced onion and cook until softened, about 3-4 minutes.
Add minced garlic and cook for 1 minute until fragrant.
Return beef tips to the skillet.
Pour in beef broth and water, then stir in Worcestershire sauce, dried thyme, dried rosemary, black pepper, and salt.
Bring the mixture to a boil, then reduce heat to low and cover. Simmer for 30 minutes until beef is tender.
In a small bowl, whisk together flour and cold water until smooth to create a slurry.
Gradually stir the slurry into the beef mixture and cook for an additional 5-7 minutes, stirring frequently, until the gravy thickens.
Remove from heat and let cool completely before transferring to freezer-safe containers.
Label and freeze for up to 3 months. To reheat, thaw overnight in the refrigerator and warm on the stove over medium heat until heated through.