The ornamental design for a base for a barstool, as shown and described.
FIG. 1 is a side elevational view of a base for a barstool, showing my new
design, the broken lines being for environmental purposes only and forming
no part of the claimed design;
FIG. 2 is a cross-sectional view taken from line 2--2 in FIG. 1; and,
FIG. 3 is a perspective view of a second embodiment.