Place a quadruple layer of paper towels on a cutting board and set aside. Place a fine-mesh strainer in the sink. Heat the oil in a large straight-sided frying pan over medium heat until shimmering. Add the carrot, onion, garlic, measured salt, and measured pepper and stir to combine. Cook, stirring occasionally, until the vegetables have softened, about 6 minutes. Transfer to a large bowl and set aside. Return the pan to medium heat, add half of the spinach, season with salt and pepper, and stir to combine. Cook, tossing occasionally with tongs, until the spinach is completely wilted, about 4 minutes. Add the remaining spinach and cook, tossing occasionally, until completely wilted, about 3 minutes more. Transfer the spinach to the strainer in the sink. Using a ladle, press on the spinach to squeeze out as much liquid as possible. Place the spinach on the layered paper towels, cover with a second quadruple layer of paper towels, and press any additional liquid out of the leaves. Discard the paper towels, finely chop the spinach, and transfer it to the bowl with the vegetables. Add the scallions, sour cream, mayonnaise, Worcestershire, and lemon juice and stir to combine. Cover tightly and refrigerate until the flavors meld and the dip is thoroughly chilled, about 2 hours. Taste and season with salt and pepper as needed, then transfer to a serving dish. Serve with saltine or Ritz crackers, crostini, carrot sticks, celery sticks, or thick-cut potato chips.