In a small bowl, mix the olive oil, garlic, salt, and pepper. Using a pastry brush, spread the mixture all over the Boston butt.
Place the meat on a rack inside a roasting pan. Roast in the oven at 200°C for 20 minutes, then reduce the heat to 160°C. Continue roasting for about 4 hours, or until the meat is tender and easily pulls apart with a fork. Once done, remove the pork from the oven and let it rest for about 30 minutes, until cool enough to handle.