Pour beef bone broth in a bowl and sprinkle gelatin in, stirring. Set aside.
Set Instant Pot to SAUTE. When display reads HOT, add oil and bacon pieces. Cook 3-4 minutes until cooked through. Transfer with a slotted spoon to a small bowl.
Season beef slabs aggressively with salt and pepper. Add as to pot and sear on all sides, about 5 minutes per side. If not all the beef slabs can fit along the bottom of the pot at one time, sear in two batches. Transfer to a rimmed baking sheet.
Add red wine to pot and scrape-up brown bits of goodness from the bottom. Simmer for around 5 minutes to reduce. Add reserved beef-gelatin broth, tomato paste, soy sauce and fish sauce, if using. Gradually whisk in flour.
Cut reserved meat into 2-inch chunks. Stir in beef cubes and juices, bacon, carrots, onions, mushrooms, potatoes, garlic, thyme, and a little more salt and pepper. Cover and set to PRESSURE COOK. Set time to 45 minutes.
Let natural release go for 10 minutes. Then turn valve to VENT to do a quick release until pin drops. Remove cover and select SAUTE again and let it thicken a bit. If more liquid-y that you'd like, stir in a slurry of 1 tbsp cornstarch or flour mixed with 2 tbsp water and stir for a minute-or-two. Transfer to a large bowl and garnish with chopped parsley on top. Serve atop buttered egg noodles, a hearty country bread or baguette for dunking, and a red Burgundy wine (for drinking).