Set EGG for indirect cooking at 375°F/177°C.
Trim of silver skin or any extra fat (optional, I prefer to keep most of fat on there.)
Truss lamb to stay together during cooking process and place in a plastic container. Set aside.
In a medium bowl, combine the butter, herbs, garlic, olive oil, zest, spices and lemon juice. Using the back of a fork mix very well until all of the butter clumps are gone and you are left with smooth mixture. Set 1⁄4 cup of the mixture aside.
Sprinkle the lamb with salt and then rub the herb mixture onto the lamb and place into a roasting pan that fits on the EGG.
Half the extra lemon and place that cut side down on the roasting pan next to the lamb along with the halved garlic bulb (facing cut side up).
Roast for 1 1⁄2 hours or until the internal temperature reads 130°F/54°C when a thermometer is inserted into the thickest part of the roast. (130°F/54°C will be Medium Rare.)
Spoon the drippings onto lamb every 20-30 minutes while it is cooking.
(Optional) About 10 minutes before the lamb is cooked, spoon the rest of the mixture onto the lamb. Optionally, spoon extra mixture onto lamb as it is sliced.
Squeeze the garlic and extra lemon onto lamb before serving it (Optional.)