Harper Lee does not provide the reader with a complete description of Miss Maudie's physical appearance in To Kill A Mockingbird. However, if you look closely throughout the text, there are several hints, clues, and short descriptions that tell us some of her physical details.
As far as her attire is concerned, Miss Maudie appears in one of two states. When she is working in her garden, she wears men's coveralls and a straw hat. However, in the evenings, after she has bathed, Miss Maudie is transformed into a "magisterial beauty." By this, we can assume that she dresses as a proper Southern lady would after her chores in the garden are finished.
We also learn in chapter 5 that Miss Maudie wears dentures. When she smiles at Scout, she reveals "two minute gold prongs clipped to her eyeteeth." In a gesture that Scout interprets as signifying friendship, she even thrusts out her bridgework.
In chapter 10, we get a further clue as to Miss Maudie's age. Scout tells Miss Maudie that everybody in the neighborhood is old, even her and Atticus who is fifty. Miss Maudie responds with a hint of indignation that fifty is not old. This comment indicates that she and Atticus are about the same age.
Another bit of information concerning Miss Maudie's physical appearance also appears in chapter 10. Scout is playing with her air rifle aiming it at Miss Maudie's rear end. She describes this as a "generous target." We also learn in chapter 13 that her shoulder "stoops," which is a family trait of hers. In chapter 16, it is mentioned that she wears glasses.