Prepare the ingredients for Lebanese garlic sauce by gathering 3 heads of peeled garlic, 5 cups of vegetable oil, 1 freshly juiced lemon and 1 teaspoon of salt. Have all of the ingredients at room temperature before you begin cooking.
Prepare a large food processor and make sure that the heads of garlic are large enough to not get caught underneath the blades. Begin by adding the garlic and salt to the food processor and running it for 20 seconds. Remove the garlic from the sides and prepare again, running the food processor again for 20 seconds and repeating as necessary until the garlic is pasty.
Keep the processor on and add the oil at a very slow rate until the garlic emulsifies into a paste. Add the lemon juice and leave the processor on for a little bit until the juice is absorbed. Add all of the ingredients as slowly as possible and in as thin of a stream as possible as the processor runs to avoid turning the mixture into a liquid. The process takes about 10 minutes; once it is done, place the mixture in a cool bowl and let it cool in the fridge before serving.