The ornamental design for a flexible oilpouch, as shown and described.
FIG. 1 is a perspective view of a flexible oil pouch showing our new design;
FIG. 2 is a top view thereof;
FIG. 3 is a bottom view thereof;
FIG. 4 is a front view, the back view being a mirror image thereof; and,
FIG. 5 is a right side view, the left side view being a mirror image thereof.
The dash-dot-dash lines shown in the drawings are for environmental structure only and form no part of the claimed design. The dashed lines shown in the drawings depict the contours of the flexible oil pouch and are for environmental structure only and form no part of the claimed design.