Heat grill to medium heat and oil the grates with cooking spray.
Add the sliced potatoes to a rimmed tray or baking dish. Sprinkle with salt and pepper on both sides. Pour 1/2 cup Garlic Oil over the potatoes and toss gently to coat. Add the potatoes to the hot grill, then brush with the remaining oil mixture. Grill, flipping the potatoes once, until golden brown, about 5 minutes per side.
Mash together the garlic and 1/2 teaspoon salt with a knife or bench scraper on a cutting board until it is a paste. Add the garlic to a small saucepan with the oil, chives, parsley, lemon juice and remaining 1/4 teaspoon salt. Cook over medium-low heat until the ingredients have combined, 3 to 4 minutes. Use as a marinade for potatoes, brush on rolls before toasting or brush on proteins for extra flavor.