Have the butcher cut a whole tenderloin in half so that you can purchase the thick end. (They will usually cut the rest into steaks.) Or buy a "butt beef tenderloin."
Salt and pepper the whole tenderloin thoroughly. Lay the bacon strips out on a clean work surface, touching each other, so they create a rectangular sheet of bacon. Lay the whole tenderloin across the bacon and carefully wrap the bacon ends over the top. Secure the bacon strips by "sewing" toothpicks through the ends.
Heat a large skillet to medium-high heat. Place the whole tenderloin, toothpick-side-down, in the skillet. Brown the bacon on all sides, turning as needed, 8-10 minutes total. (This can be done ahead and the seared tenderloin, can then be refrigerated for a 1-2 days if needed.)
Place the thinly sliced fennel and garlic in a 6-quart slow cooker. Set the seared beef tenderloin on top and pour the pan drippings over the top. Drizzle the broth, honey, and Worcestershire sauce over the tenderloin.
Insert an oven-safe meat thermometer in the thickest part of the whole tenderloin, then cover and turn the slow cooker on low. A crockpot beef tenderloin will be perfectly medium-rare when the temperature reaches 130 degrees F, about 2-4 hrs, depending on weight and thickness. Make sure to check the tenderloin at the 2 hour mark, and every 20 minutes after until it reaches the desired temperature.
At 130 degrees F, remove the whole tenderloin and cover with foil for at least 10 minutes. The temperature will continue to rise to 135 degrees as it rests.
To serve, remove the toothpicks and slice the tenderloin into thin rounds. Top with honey garlic glaze.
If you want to thicken the sauce, remove the tenderloin and whisk 1 tablespoon flour into the slow cooker. Cover the tenderloin with foil and simmer the sauce another 20-30 minutes. Or to thicken quickly, pour the juices in a skillet and whisk with flour over medium-high heat.Serve with roasted potatoes, duchess potatoes, or perfect mashed potatoes!