Add the bacon to the crockpot and set on the medium saute setting. Cook the bacon until crisp, about 3 minutes.
Remove and drain on paper towels and set aside. When cool, crumble the bacon.
Toss the beef with the flour and season with salt and pepper. You can do this in a bowl, or add the flour, salt, and pepper to a Ziploc back and add the beef in batches. Shake the bag to coat the beef.
Add the beef to the crockpot in batches and brown the beef on both sides, keeping the crockpot set to the medium saute setting.
You want a nice sear on the beef. The beef is ready to turn when it easily releases from the bottom of the pan. Remove the beef as it browns and set aside.
After browning all the beef, add the onions keeping the crockpot on the "saute" setting. Cook, stirring frequently, for about 15 - 20 minutes until the onions are soft and and golden brown.
Add the garlic and cook for another minute.
Add ½ of the beer and stir, scraping the bottom of the pan. Let reduce for about 4 minutes.
Add the stock, brown sugar, cider vinegar, thyme, bay leaf, and tarragon and stir to combine.
Add the beef back to the crockpot and stir to combine.
Put the lid on the crockpot and change the setting to slow cook, medium for 3 hours. If you crockpot does not have a medium setting, set to high and check the stew after 2 hours for tenderness.
When the stew is tender, remove the lid from the crockpot and taste, adding more salt and pepper as needed.
Stir in the bacon.
Serve over noodles, rice or with a side of bread to sop up the sauce.