Whisk the ketchup, water, apple cider vinegar, brown sugar, onion powder, garlic powder, salt, and hot sauce together in a small saucepan. Bring to a gentle simmer over low heat for 5 minutes. Remove from heat and let cool slightly to thicken.
In a crockpot, bring the beef broth, onion powder, garlic powder, liquid smoke and Worcestershire sauce to a low simmer on low to warm heat.
Submerge the shaved roast beef into the simmering broth for 60 minutes. Remove with tongs, letting excess liquid drain back into the pan.
Optionally steam or lightly toast the buns. Layer the warm roast beef loosely onto each bottom bun (fluffing it rather than laying it flat captures the signature texture). Top with sauces.