Preheat a wood oven to 500 degrees F. Alternately, preheat a regular oven to 450 degrees F.
In a large bowl, toss the Brussels sprouts with 2 tablespoons olive oil.
Place two 12-inch cast-iron pans in the oven. Once hot and smoking slightly, remove and add 1 tablespoon blended oil to each and dump in the sprouts, splitting them between the 2 pans.
Roast the Brussels sprouts, tossing periodically, until crisp and lightly browned, about 10 minutes.
Meanwhile, in a large bowl, whisk together the lemon juice, salt, red pepper flakes, garlic and remaining 1/4 cup olive oil to form a dressing.
In a small skillet over medium heat, heat 1/3 cup blended oil. Once the oil is hot, fry any reserved Brussels sprouts leaves until evenly browned and crispy, about 40 seconds. Drain on a paper towel-lined sheet tray and salt while still warm.
Toss the roasted Brussels sprouts with the dressing. Transfer to a platter and top with the crispy sprout leaves and a sprinkling of pepper. Serve hot.