Preheat oven to 450 F.
Place pork shoulder on a rack in a roasting pan.
Mix garlic, salt, pepper, thyme, oregano and olive oil in a small bowl.
Rub all over the pork shoulder.
Roast, uncovered, at 450 F for 45 minutes.
Remove the pork shoulder from the oven; decrease heat to 225 F.
Add sliced onions, chicken broth, beer and chili flakes to the bottom of the roasting pan. Baste the pork with the pan liquids.
Tent tin foil over the roast and return to the oven. Check every hour or so and baste the roast with liquids from the pan; add more chicken broth if needed.
Roast about 7 to 8 hours, basting every hour.
The roast is done when the internal temperature is 170-175 F.
Let the roast rest for 20-30 minutes. Remove skin and fat before carving.
