FIG. 1 is a front perspective view of a combined square base and cover showing a first embodiment of our new design;

FIG. 2 is a front view thereof, shown in an enlarged scale;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top plan view thereof, shown in an reduced scale;

FIG. 7 is a bottom plan view thereof;

FIG. 8 is a front perspective view of a combined square base and cover showing a second embodiment of our new design, shown in an enlarged scale;

FIG. 9 is a front view thereof;

FIG. 10 is a rear view thereof;

FIG. 11 is a left side view thereof;

FIG. 12 is a right side view thereof;

FIG. 13 is a top plan view thereof, shown in an reduced scale; and,

FIG. 14 is a bottom plan view thereof.

The broken lines illustrate environmental elements of the combined square base and cover which form no part of the claimed design.