The word "flanked" means to be positioned at the side of something or someone. Its antonyms would be words that mean the opposite, such as central, uncovered, alone or isolated. If something is central, it is located in the middle or at the center of a larger area, and is not on the side. Uncovered means not covered, hidden, or protected by something else. If someone is alone or isolated, they are not surrounded by others on either side. Thus, these words mean the opposite of "more flanked" and suggest a sense of being less surrounded or less at the side of something.