Heat olive oil in a large skillet over medium-high heat.
Add beef sirloin tips to the skillet and brown on all sides, about 3-4 minutes per side.
Transfer the browned beef tips to the crock pot.
In the same skillet, add diced onion and minced garlic. Sauté for 2-3 minutes until softened and fragrant.
Add the sautéed onions and garlic to the crock pot with the beef.
Pour beef broth and Worcestershire sauce into the crock pot.
Sprinkle salt, black pepper, dried thyme, and dried rosemary over the ingredients in the crock pot.
Stir gently to combine all ingredients.
Cover and cook on low for 6 hours or until beef is tender.
About 30 minutes before serving, melt butter in a small pan over medium heat.
Add almond flour to the melted butter and whisk continuously for 1-2 minutes to create a roux.
Slowly add the roux to the crock pot and stir well to thicken the gravy.
Add heavy cream to the crock pot and stir to combine.
Cover and cook on low for an additional 30 minutes until gravy is thickened.
Serve hot over cauliflower rice or mashed cauliflower.