Container for packaging units

A method comprising:

• receiving a body that comprises a lower surface, an upper rim, and a plurality of side walls that extend between the lower surface and the upper rim, wherein the upper rim defines an opening to an interior space of the body, and wherein at least one side wall of the plurality of side walls comprises one or more first apertures that extend through the at least one side wall, and the lower surface comprises one or more bottom apertures that extend through the lower surface;
• and
• covering the opening of the body with a flexible cover that is bonded to the body along the upper rim, the flexible cover comprising an insert formed in the flexible cover and a gas-impermeable material that encircles the insert, the insert comprising a first gas-permeable material through which gas can enter and exit the interior space of the body;
• and
• covering the one or more first apertures and the one or more bottom apertures with a second gas-permeable material connected to the body, wherein gas can enter and exit the interior space of the body through the second gas-permeable material, wherein the upper rim of the body is spaced apart from any of the first gas-permeable material and the second gas-permeable material.