Cool the brownies completely
Cut into the sizes you will want when defrosted.
if frosted: flash freeze by putting them in a single layer on a cookie sheet and popping it into the freezer for an hour or so. This will make the frosting stiff so it won't smear when wrapping.
Tear off a sheet of plastic warp large enough to completely cover each individual brownie.
Lay the plastic on the counter and place a brownie in the center.
Wrap the plastic totally around the brownie and secure it.
optional: for extra protection you can repeat this with a second layer of plastic wrap and/or aluminum foil.
Repeat wrapping for each brownie.
Stick all of your wrapped brownies into a freezer bag or airtight container. Seal the bag by pressing all of the air out of it and zipping it closed. Or, by putting the lid on the top of the container.
Write the date on the container or bag and place it into the freezer