Pat pot roast dry. Coat beef on all sides with flour. Season beef generously all over with salt and pepper. Heat oil in Dutch oven over medium-high heat. Add roast, brown well on all sides, about 10 minutes. Remove roast from pan. Transfer beef and any juices to slow cooker.
Add gingerroot, rice vinegar, garlic, chili flakes, soy sauce, Kecap Manis and 1 cup water to Dutch oven. Cook, stirring to remove any brown bits from bottom of pan. Pour over beef in slow-cooker. Cover and cook on LOW for 6 to 8 hours until roast is fork-tender. Remove roast to cutting board, tent with foil.
Transfer sauce to saucepan and cook over high heat to thicken by reducing by half, about minutes. You should have about 1-1/2 cups of sauce. Carve roast across the grain and serve with sauce as a dip and along with the Asian Slaw (recipe follows).