In a small bowl, whisk together the broth, soy sauce, minced onion, garlic powder, salt, black pepper, oregano, thyme, bay leaf, and red pepper flakes. (Freezing instructions begin here.)
Place the roast in the cooker; season lightly, with salt and black pepper, on all sides.
Pour the sauce over the top; cover and cook, on low for 8 to 10 hours or on high for 5 to 6 hours, until the meat easily shreds.
Transfer the roast to a cutting board and shred with two forks.
Return the meat to the cooker and stir it into the sauce.
Spread a thin layer of butter over one side of each slice of bread.
Place a slice of cheese on the unbuttered side of half the slices of bread.
Using a slotted spoon, add a layer of the shredded meat – be sure to drain the liquid first.
Top with another slice of cheese and a second slice of bread, buttered-side up.
Heat a large skillet or griddle over medium heat.
Cook the sandwiches for a few minutes, on each side, until the bread is golden brown and the cheese has melted.
Serve the sandwiches warm, with the warmed juices, from the cooker, in small bowls alongside for dipping.
