The ornamental design for a flower basket candle, as shown and described.
FIG. 1 is an elevational view of the flower basket candle of the ornamental design, the front, side and rear views of the ornamental design being the same;
FIG. 2 is a plan view of the flower basket candle of the ornamental design; and,
FIG. 3 is a bottom view of the flower basket candle of the ornamental design.