Wash meat with warm water. If the fat cap is more than about 1/2" thick, trim it down to that. Cut garlic into large slivers. Place meat on cutting board, fat side up. Using a sharp knife, insert slivers of garlic under the fat, distributed evenly. Rub liquid smoke into meat.
Place meat, fat side up, on rack in roasting pan. Roast at 450 for 15 minutes. Reduce heat to 350F, open door of oven to reduce temperature to 350 or so, then close door. Roast for another 25 minutes.
The timings above are very rough. That timing is for rare meat out of a 3-lb. roast. For smaller roasts, or for very rare meat, cut down the cooking time. This roast is very good surprisingly rare, but be careful about meat quality if so. Most prefer medium rare to medium; if so, add another 5-15 minutes to the cooking time.
If you have the time, prepare the meat ahead of time and let it marinate with the garlic and liquid smoke. Eight hours is plenty of time.
Optionally, roasted potatos are nice and easy to make at the same time. Wash, then cut 2 or 3 medium baking potatos into 1" cubes, leaving the skin on. Dredge potatos with oil and spices. Place potatos in roasting pan before inserting the rack/meat. The potatos should cook for about 50-60 minutes. Note that this is longer than the meat, in general, so they need to be inserted earlier. While cooking in the same pan is traditional, I prefer them in a separate pan; they are far more crisp and less greasy that way. They will need to be turned once or twice so that they don't stick.
The roast is great hot and even better chilled and cut thinly for sandwiches the next day.