I claim the ornamental design for a hoof boot sole, according to the present design as shown and described.
FIG. 1 is a top plan view of the hoof boot sole according to the present design;
FIG. 2 is a front view thereof;
FIG. 3 is a side elevation view thereof, the opposite side being a mirror image;
FIG. 4 is a rear view thereof; and,
FIG. 5 is a top perspective view thereof.
In FIGS. 2, 3, and 4, the portions of the hoof boot above the sole are not claimed. As such, the side walls and upper portion of the hoof boot are depicted in dotted lines. Moreover, FIGS. 2, 3, and 4 include dot-dash lines to depict the claimed and unclaimed boundary. Specifically, the side walls of the hoof boot are not claimed except for the grooves dipping down from the top surface.