I claim the ornamental design for a fence post anchoring structure, as shown and described.
FIG. 1 of the drawings is a perspective view showing the front, right side, and top of a fence post anchoring structure embodying the design of my invention;
FIG. 2 is a front elevation view of the fence post anchoring structure;
FIG. 3 is a left side elevation view;
FIG. 4 is a right side elevation view;
FIG. 5 is a back elevation view;
FIG. 6 is a top plan view with a welded-on fence post supporting component added in broken lines to indicate a typical environment;
FIG. 7 is a bottom plan view;
FIG. 8 is a perspective view similar to FIG. 1 with a welded-on fence-post-supporting component added in broken lines to indicate a typical environment; and,
FIG. 9 is a right side elevation view similar to FIG. 4 with the fence-post-supporting component added in broken lines.
The broken lines are included for the purpose of illustrating environment and form no part of the claimed design. The appearance of the article between the break lines forms no part of the claimed design.