FIG. 1 is a left side elevational view of a flexible sole for athletic shoe showing my new design;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a front elevational view thereof.

The broken-line showings of a shoe in FIGS. 1, 3 and 5-6 are environmental only and form no part of the claimed design.