Puree 2 garlic cloves in a food processor with 1/4 cup olive oil. Add 1 chopped scallion, 2 teaspoons white vinegar and 1/4 teaspoon each cumin seeds and red pepper flakes; pulse until combined. In batches, cook one 16-ounce package thawed frozen tostones (fried plantains) in vegetable oil until golden and crisp, 2 to 4 minutes per side. Blot with paper towels and season with salt. Serve with the garlic sauce.