The subject invention is a lid assembly (20) for use on a container (22) presenting an endless top rim (24). A frame (26) includes shell-shaped sidewalls (36) that face one another, and present upper concave central edges (48). The upper concave central edges (48) are connected by lower edges (50) to define opposed L-shaped openings (54) between the central edges (48). A pair of abutting L-shaped flaps (28) each define a top leg (64) and a side leg (68). The flaps (28) are complementary to the L-shaped openings (54) by extending away from each other along the upper central edges (48) of the sidewalls (36) and then downward to the lower edge (50). The top legs (64) may be pushed down into the opening (54) to provide access to the container (22) while the side legs (68) bias the flaps (28) to a closed position.