In a large bowl, combine the top sirloin roast with soy sauce, salt, black pepper, and crushed allspice berries. Marinate for at least 3 hours or overnight in the refrigerator.

Heat vegetable oil in a heavy-bottomed pot or Dutch oven over medium-high heat. Sear the marinated roast for about 4-5 minutes on each side until golden brown.

In the same pot, add more oil if needed, then sauté the chopped onion, celery, and minced garlic for 4-5 minutes until soft.

Pour in the beef broth, scraping the bottom to release browned bits, then return the seared roast and add enough water to partially cover it.

Reduce heat to low, cover, and cook for 2.5 to 3 hours, checking occasionally.

About 30 minutes before cooking time is up, add baby potatoes to the pot, stirring gently to ensure they are submerged.

Remove pot from heat and let the roast rest for about 10 minutes before slicing and serving with the potatoes and gravy.